Apache - multiple virtual servers but one constantly locks up

Hi there. I am having a bit of a problem with apache.

I am running 3 websites from my server: GLPI (Helpdesk), OCS Reports, and Centreon. GLPI is configured with AutheNTLM to use NTLM pass through authentication (whether this is relevant or not I do not know...).

The problem is, GLPI will stop responding in the middle of the day. Its not consistent so it happens at random times (usually once a day). Looking at the cpu/memory I can not really see anything that is out of the ordinary. If i restart the apache service, it begins working again until once again it refuses to load.

Can someone please tell me where I should begin to troubleshoot this issue? I would think its an overall apache problem but why would my other sites work fine?

Hi,

check the apache error logs while the program stops responding ..
that will give you a clue why the program is not responding .