Dear Shanti,
yes I saw APC is included, I disabled it because I had problems when content changed and the cache didn't recognize it - I'll have a deeper look into it.
AFAIK eAccelerator doesn't work with php 5.2.0.
(Yesterday a zpool on my new SC 3.2 crushed with all my webdata, so currently I'm having other things to fix :-((( )
In your /opt/coolstack/php5/lib/php.ini file, change the options for apc.stat to be:
apc.stat=1
This disables caching, which will slow down performance on a heavy loaded box, but is a necessity for development. You'll need to restart apache after making this change.
Cheers-
John