Internal Server Error with latest dev 22 Dec 2012

Hello,

Got the 500 Internal Server Error with latest dev 22 Dec 2012. Pls note that for testing, we installed D7.18 on the same server/user, went smooth, no errors. Other Drupal 6 & 7 installs are also working w/o errors.

Server: dedicated, PHP 5.2.17, CentOS

Some scripts on our server are not yet ready for for php 5.3, hence have not tried that.

initially thought it was re clean urls, tried changes to .ahtaccess and settings.php files. No good.

Asked our host for help. their respnes is;
"error log shows premature end of script headers only with no other error.

I found http://drupal.org/node/213260

Tried one suggestion but failed:

in /home/csi/public_html/julio-dev
cat php.ini
max_execution_time = 1600 ; Maximum execution time of each script, in seconds
max_input_time = 1600 ; Maximum amount of time each script may spend parsing request data
memory_limit = 80M ; Maximum amount of memory a script may consume (8MB)

post_max_size = 80M
extension=pdo.so
extension=pdo_sqlite.so
extension=sqlite.so
extension=pdo_mysql.so

If more errors can be displayed that would be helpful. As of right now there is really nothing to work out of. I would suggest trying php 5.3"

Any thoughts? Thanks.