I've been using Turck-mmcache with my LAMP test server; it seemed to work great until I did the latest CVS update. I kept getting error messages about "redeclaring ...dynalink" filter. Turned off Turck, and all worked fine. (I just had to play around with the TeX....and now, I don't want to lose either!)
Anyone found a fix for Turck? Perhaps there's a better PHP accelerator I should be using?
Make sure you clear your cache when you upgrade Moodle code. I never got Turck working properly last time I tried (a couple of months ago) so I'm still using PHP Accelerator.