I'm experiencing a problem with a php/apache install on debian lenny. At random times during the day it will stop servicing request for .php pages, but static pages (html/css etc.) continue to work. There is no useful information in the apache or php error logs. There are ~40 sites running on this server, so I can't even tell which site is causing the problem.
Does anyone have nay ideas on how to troubleshoot this problem?