This is pretty strange situation I am getting.
I have installed apc (with ./configure and make) on my LAMP gentoo with PHP 5.2.
To get apc loaded i need to place apc.so in my www php directory otherwise it just don't get loaded.
I don't even any idea of this, if you have even only tips please post an answer.
If you need the full series of command it's here: Failed installing APC?