php problem ???

[DmT]

hi, i have a server with ispCP
all works fine, but, when you try todo a large query with php, the cpu load go to critical, to try to get where is the problem, i install monit, and the problem its the php configuration, apache goes down, but all the other services are working ok, i host 5 invision forums, when i try to send a mail to my user the apache (php) fails....

*Server :

Amd Opteron Dual Core 1210 1.8 ghz
2 gb ram
400 gb hdd