Recently, Derek and I were running into problems with CGI errors on our development server for NFI Studios. We had recently upgraded our PHP install from 5.0 to 5.2, so we started looking for differences between the two.
After a brief search on Google, I came up with a German forum with a potential solution: APC (Alternative PHP Cache). It turns out that Caching for PHP 5.2 is different than for PHP 5.0. So, I turned of APC (by editing the php.ini file).
For all of you coders out there, just an FYI.