Page not found - URGENT

Hello?
The question is, may so trivial problem, and, I don´t identify where it may come from, if it could be PHP o something in the application.
Someone is not translating 3Fs 3Ds per ? or =
Any ideas?

Hi all, I ask your help,
just a day looking around, almost everywhere, Drupal posts, PHP, htaccess (didn´t change last month - using clean URLs), common.inc, settings. I´m going to sleep and have nice %3F and %3D dreams.
But, I´m not surrended.
Making a summary, %3D and %3F referred in URL results in a page not found. May be there is a workaround to fix it, something in htaccess or an urldecode somewhere.
Someone can help?

my .htacces is as follows, nothing special, just copied an pasted from Clean Urls recommendations

#
# Apache/PHP/Drupal settings:
#

# Protect files and directories from prying eyes.
<FilesMatch "(\.(engine|inc|install|module|sh|.*sql|theme|tpl(\.php)?|xtmpl)|code-style\.pl|Entries.*|Repository|Root)$">
  Order deny,allow
  Deny from all
</FilesMatch>

# Set some options.
Options -Indexes
Options +FollowSymLinks

# Customized error messages.
ErrorDocument 404 /index.php

# Set the default handler.
DirectoryIndex index.php

# Override PHP settings. More in sites/default/settings.php
# but the following cannot be changed at runtime.

# PHP 4, Apache 1
<IfModule mod_php4.c>
  php_value magic_quotes_gpc                0
  php_value register_globals                0
  php_value session.auto_start              0
</IfModule>

# PHP 4, Apache 2
<IfModule sapi_apache2.c>
  php_value magic_quotes_gpc                0
  php_value register_globals                0
  php_value session.auto_start              0
</IfModule>

# PHP 5, Apache 1 and 2
<IfModule mod_php5.c>
  php_value magic_quotes_gpc                0
  php_value register_globals                0
  php_value session.auto_start              0
</IfModule>

# Reduce the time dynamically generated pages are cache-able.
<IfModule mod_expires.c>
  ExpiresByType text/html A1
</IfModule>

# Various rewrite rules.
<IfModule mod_rewrite.c>
  RewriteEngine on

  # If your site can be accessed both with and without the prefix www.
  # you can use one of the following settings to force user to use only one option:
  #
  # If you want the site to be accessed WITH the www. only, adapt and uncomment the following:
  # RewriteCond %{HTTP_HOST} !^www\.example\.com$ [NC]
  # RewriteRule .* http://www.example.com/ [L,R=301]
  #
  # If you want the site to be accessed only WITHOUT the www. , adapt and uncomment the following:
  # RewriteCond %{HTTP_HOST} !^example\.com$ [NC]
  # RewriteRule .* http://example.com/ [L,R=301]


  # Modify the RewriteBase if you are using Drupal in a subdirectory and
  # the rewrite rules are not working properly.
  #RewriteBase /drupal

  # Rewrite old-style URLs of the form 'node.php?id=x'.
  #RewriteCond %{REQUEST_FILENAME} !-f
  #RewriteCond %{REQUEST_FILENAME} !-d
  #RewriteCond %{QUERY_STRING} ^id=([^&]+)$
  #RewriteRule node.php index.php?q=node/view/%1 [L]

  # Rewrite old-style URLs of the form 'module.php?mod=x'.
  #RewriteCond %{REQUEST_FILENAME} !-f
  #RewriteCond %{REQUEST_FILENAME} !-d
  #RewriteCond %{QUERY_STRING} ^mod=([^&]+)$
  #RewriteRule module.php index.php?q=%1 [L]

  # Rewrite current-style URLs of the form 'index.php?q=x'.
  RewriteCond %{REQUEST_FILENAME} !-f
  RewriteCond %{REQUEST_FILENAME} !-d
  RewriteRule ^(.*)$ index.php?q=$1 [L,QSA]
</IfModule>

# $Id: .htaccess,v 1.73 2006/04/14 09:08:26 killes Exp $

Any ideas? The problem is still there.
Regards, Gustavo

I'm so bored looking for this in "my issues" for 22 days and without any answer.
Happy new year!
Gustavo