500 Internal Server Error when updating templates
 

All of a sudden I seem to be getting blank blue screens inside of AdminCP when I update templates. I don't recall anything new being installed on the server that would cause this (but we do update the OS frequently, which in turn updates Apache & PHP - so I'm not ruling anything out here). When I investigate the server logs I see that my update request is generating a 500 Internal Server Error and I can't track down the cause. I've disabled mod_security and that does not solve the problem. Here's the apache log:

- - - [16/Jul/2010:11:15:45 -0500] "POST /forum/admincp/template.php?do=updatetemplate HTTP/1.1" 500 1526 "http://www.domain.com/forums/admincp/template.php?s=&do=edit&templateid=3257&group=all& searchstring=xxxxx&expandset=all" "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2.6) Gecko/20100625 Firefox/3.6.6 GTB7.0"

Any thoughts or suggestions? I've tried everything I can think of to no avail. Thanks!