I misunderstood.
To restate:
I checked all permission - correct. Host even has a script to check that. (permissions are correct, when i upload a phpinfo file to the same directory it works correctly -as other person has too.)
I placed a phpinfo file in the directory and it worked
I recomplied apache - no change
I restored a version of php.ini from before the apache rebuild - no change
I did a check of all mysql databases -all were ok
I rebooted the computer - no change
I reinstalled a new download direct from the website - no change
I created a new installation - no change
I manually updated ImageMagick - as server is Centos and their version is ancient - no change
I tried putting:
error_reporting(E_ALL);
ini_set('display_errors', '1');
Into the top of login.php and index.php - did not show anything
I tried:
php_flag log_errors on
php_value error_log /home/path/public_html/domain/PHP_errors.log
in the .htaccess file (of course with the correct domains and paths
Other sites and scripts that use php are working just fine, i.e. the sample I have
http://surrealsf.com/photos, the main site is php. Wordpress and other installs run fine.
Logs are no where near 2 gigs, as that can cause apache to choke.
Suexex logs show nothing.
Only errors shown are premature, 500 and 404 for the error document, as I removed it to debug.
I am running version 1.5.20, and php and mysql are fine, they have not been updated since the past weekend when they all worked fine. All that has been updated recently:
tail /var/log/yum.log
Dec 04 13:43:01 Updated: tzdata-2012i-2.el5.i386
Dec 04 13:43:02 Updated: newrelic-daemon-3.1.5.120-1.i386
Dec 04 13:43:06 Updated: newrelic-php5-3.1.5.120-1.i386
Dec 05 23:17:08 Installed: kernel-PAE-2.6.18-308.24.1.el5.i686
Dec 05 23:17:09 Updated: kernel-headers-2.6.18-308.24.1.el5.i386
Dec 05 23:17:19 Installed: kernel-PAE-devel-2.6.18-308.24.1.el5.i686
Dec 05 23:17:25 Installed: kernel-2.6.18-308.24.1.el5.i686
Dec 05 23:17:34 Installed: kernel-devel-2.6.18-308.24.1.el5.i686
Dec 19 02:17:14 Updated: libtiff-3.8.2-18.el5_8.i386
Dec 19 02:17:15 Updated: libtiff-devel-3.8.2-18.el5_8.i386
None of that was this weekend, and I updated libtiff after the fact.