Cached pages not being served

7.x-1.0-beta2 is the boost version.
normal drupal page caching IS disabled.

where can i set that: "Options +SymLinksIfOwnerMatch" setting in the boost config?
and then, i should remove it from the cache .htaccess file?
what are the other lines that are unnecessary in that .htaccess file (my last 5 lines)

all was working brilliantly up to 10 days ago, so i know my root .htaccess file was just fine. Since it stopped working i have tweaked the boost htaccess code by changing those boost config settings numerous times/options to see if that would help.

what might cause boost to flush the cached pages on every visit (that you said explains the recreation of the htaccess file?)

my root .htaccess file looks like this:

#
# Apache/PHP/Drupal settings:
#

# Protect files and directories from prying eyes.

Order allow,deny

# Don't show directory listings for URLs which map to a directory.
Options -Indexes

# Follow symbolic links in this directory.
# For security reasons, Option followsymlinks cannot be overridden.
#Options +FollowSymLinks
Options +SymLinksIfOwnerMatch

# Make Drupal handle any 404 errors.
ErrorDocument 404 /index.php

# Set the default handler.
DirectoryIndex index.php index.html index.htm

# Override PHP settings that cannot be changed at runtime. See
# sites/default/default.settings.php and drupal_initialize_variables() in
# includes/bootstrap.inc for settings that can be changed at runtime.

# PHP 5, Apache 1 and 2.

php_flag magic_quotes_gpc off
php_flag magic_quotes_sybase off
php_flag register_globals off
php_flag session.auto_start off
php_value mbstring.http_input pass
php_value mbstring.http_output pass
php_flag mbstring.encoding_translation off

# Requires mod_expires to be enabled.

# Enable expirations.
ExpiresActive On

# Cache all files for 2 weeks after access (A).
ExpiresDefault A1209600

# Do not allow PHP scripts to be cached unless they explicitly send cache
# headers themselves. Otherwise all scripts would have to overwrite the
# headers set by mod_expires if they want another caching behavior. This may
# fail if an error occurs early in the bootstrap process, and it may cause
# problems if a non-Drupal PHP file is installed in a subdirectory.
ExpiresActive Off

# Various rewrite rules.

RewriteEngine on

# Block access to "hidden" directories whose names begin with a period. This
# includes directories used by version control systems such as Subversion or
# Git to store control files. Files whose names begin with a period, as well
# as the control files used by CVS, are protected by the FilesMatch directive
# above.
#
# NOTE: This only works when mod_rewrite is loaded. Without mod_rewrite, it is
# not possible to block access to entire directories from .htaccess, because
# is not allowed here.
#
# If you do not have mod_rewrite installed, you should remove these
# directories from your webroot or otherwise protect them from being
# downloaded.
RewriteRule "(^|/)\." - [F]

# If your site can be accessed both with and without the 'www.' prefix, you
# can use one of the following settings to redirect users to your preferred
# URL, either WITH or WITHOUT the 'www.' prefix. Choose ONLY one option:
#
# To redirect all users to access the site WITH the 'www.' prefix,
# (http://example.com/... will be redirected to http://www.example.com/...)
# uncomment the following:
RewriteCond %{HTTP_HOST} !^www\. [NC]
RewriteRule ^ http://www.%{HTTP_HOST}%{REQUEST_URI} [L,R=301]
#
# To redirect all users to access the site WITHOUT the 'www.' prefix,
# (http://www.example.com/... will be redirected to http://example.com/...)
# uncomment the following:
# RewriteCond %{HTTP_HOST} ^www\.(.+)$ [NC]
# RewriteRule ^ http://%1%{REQUEST_URI} [L,R=301]

# Modify the RewriteBase if you are using Drupal in a subdirectory or in a
# VirtualDocumentRoot and the rewrite rules are not working properly.
# For example if your site is at http://example.com/drupal uncomment and
# modify the following line:
# RewriteBase /drupal
#
# If your site is running in a VirtualDocumentRoot at http://example.com/,
# uncomment the following line:
RewriteBase /

### BOOST START ###

# Allow for alt paths to be set via htaccess rules; allows for cached variants (future mobile support)
RewriteRule .* - [E=boostpath:normal]

# Caching for anonymous users
# Skip boost IF not get request OR uri has wrong dir OR cookie is set OR request came from this server
RewriteCond %{REQUEST_METHOD} !^(GET|HEAD)$ [OR]
RewriteCond %{REQUEST_URI} (^/(admin|cache|misc|modules|sites|system|openid|themes|node/add|comment/reply))|(/(edit|user|user/(login|password|register))$) [OR]
RewriteCond %{HTTP_COOKIE} DRUPAL_UID [OR]
RewriteCond %{ENV:REDIRECT_STATUS} 200
RewriteRule .* - [S=3]

# GZIP
RewriteCond %{HTTP:Accept-encoding} !gzip
RewriteRule .* - [S=1]
RewriteCond %{DOCUMENT_ROOT}/cache/%{ENV:boostpath}/%{HTTP_HOST}%{REQUEST_URI}_%{QUERY_STRING}\.html -s
RewriteRule .* cache/%{ENV:boostpath}/%{HTTP_HOST}%{REQUEST_URI}_%{QUERY_STRING}\.html [L,T=text/html,E=no-gzip:1]

# NORMAL
RewriteCond %{DOCUMENT_ROOT}/cache/%{ENV:boostpath}/%{HTTP_HOST}%{REQUEST_URI}_%{QUERY_STRING}\.html -s
RewriteRule .* cache/%{ENV:boostpath}/%{HTTP_HOST}%{REQUEST_URI}_%{QUERY_STRING}\.html [L,T=text/html]

### BOOST END ###

# Pass all requests not referring directly to files in the filesystem to
# index.php. Clean URLs are handled in drupal_environment_initialize().
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_URI} !=/favicon.ico
RewriteRule ^ index.php [L]

# Rules to correctly serve gzip compressed CSS and JS files.
# Requires both mod_rewrite and mod_headers to be enabled.

# Serve gzip compressed CSS files if they exist and the client accepts gzip.
RewriteCond %{HTTP:Accept-encoding} gzip
RewriteCond %{REQUEST_FILENAME}\.gz -s
RewriteRule ^(.*)\.css $1\.css\.gz [QSA]

# Serve gzip compressed JS files if they exist and the client accepts gzip.
RewriteCond %{HTTP:Accept-encoding} gzip
RewriteCond %{REQUEST_FILENAME}\.gz -s
RewriteRule ^(.*)\.js $1\.js\.gz [QSA]

# Serve correct content types, and prevent mod_deflate double gzip.
RewriteRule \.css\.gz$ - [T=text/css,E=no-gzip:1]
RewriteRule \.js\.gz$ - [T=text/javascript,E=no-gzip:1]

# Serve correct encoding type.
Header set Content-Encoding gzip
# Force proxies to cache gzipped & non-gzipped css/js files separately.
Header append Vary Accept-Encoding

order allow,deny
allow from all

deny from 61.154.226.252
deny from 184.82.29.169
deny from 205.203.134.197
deny from 208.115.111.
deny from 208.115.113.
deny from 208.138.254.150
deny from 65.94.2.225
deny from 199.21.99.125
deny from 95.108.158.241
deny from 182.118.20.
deny from 182.118.21.
deny from 182.118.22.
deny from 182.118.25.
deny from 101.226.168.
deny from 101.226.166.
deny from 101.226.167.
deny from 101.226.169.
deny from 78.30.200.81
deny from 69.30.238.26
deny from 184.154.48.82

i don't have/see that setting on my htaccess settings page: admin/config/system/boost/htaccess (see screenshot)

also, on that screenshot, be advised, i have tried every combination of settings for those first three sets of choices. the combination that USED to work (10 days ago) was the third choice for Servers URL, 2nd choice for Doc Root and 2nd choice for ETag Settings (i'm not on a server cluster). now, i can find no combo that works to serve my cached pages.

These are the last 5 lines of my cache > htaccess file.
the last line is NOT commented OUT, so that should be what you wanted me to manually set, correct? i believe it's already correct...

SetHandler Drupal_Security_Do_Not_Remove_See_SA_2006_006
Options None
# For security reasons, Option followsymlinks cannot be overridden.
#Options +FollowSymLinks
Options +SymLinksIfOwnerMatch

Also, the same goes in my root htaccess file: (it's not commented out there, either)
# Follow symbolic links in this directory.
# For security reasons, Option followsymlinks cannot be overridden.
#Options +FollowSymLinks
Options +SymLinksIfOwnerMatch

And, yes, i CAN manually type in the URL of my cached pages and they show up just fine.
However, very rarely I do get a 500/internal server error when trying to load different pages on the site. Then a refresh brings the page up. What should those settings be to not get the intermittent 500 error? I've tried the recommended settings and then the 500 error happens very frequently. That's what caused me to use other settings.

Should i be using the dev version of Boost?

Will let you know what happens tomorrow, if my cache htaccess file gets re-created again...
Thanks for your help.

Most pages on site are being served correctly as cached pages, but only for one day, even though I have Max Cache Lifetime set at 3 weeks. The next morning, the pages re-cache as they are visited for the first time.

Steps taken:
I've upgraded to the dev version of boost: 7.x-1.0-beta3+12-dev, and i selected the option at bottom of htaccess config page (attached screenshot), so that now the last THREE lines of my cache .htaccess file look like this:

SetHandler Drupal_Security_Do_Not_Remove_See_SA_2006_006
Options None
Options +SymLinksIfOwnerMatch

Pages are all caching fine, but here are the things that are still wonky:
1. The htacccess file is recreated at each cron run (every 3 hours). At least the TIMESTAMP on the .htaccess file changes every 3 hours to be the same time as the most recent cron run. (Is that supposed to happen? I don't think it was happening before...)
2. It seems the whole site is being served as cached pages for one day. The home page re-caches itself every morning the very first time I visit it, even tho it is set to expire in 3 weeks, just like all other pages on site. (Max Cache Lifetime = 3 weeks). The other pages remained cached a little longer (for me) until someone else visits the page, then those pages are re-cached.

Thoughts?
Thanks again!
Jean