Apache or php-fcgi freeze

[Elf]

Hello,

I'm using the ispCP panel since last 4 months, and since almost begining I got a problem with the one of listed in topic features.
Maybe I am a little bit newbie, but I've searched logs many times and didnt found anything which could help me to solve it.
It goes like this:

Server runs for *some* (sometimes 2, sometimes 30) hours, and then, it somehow freezes, because in process list it does whole time works.
It happens mostly to one client, but sometimes to whole server.

I was whole time restarting the apache manually, but I'm already a little bit bored so, if anyone could help me, I would be thankfull.