System Freezes

I'm running IDS 11.50.FC6 on HPUX 11.31. We recently rolled out an internally developed web-based system (Apache perl/mod_perl) and immediately started noticing that our HPUX system becomes completely unresponsive, for 20-30 seconds at a time, many times throughout the day. My first thought was network problems, but we have pretty much ruled this out since I can connect to a twin HPUX server which seems fine during the outages. During these system freezes, any connections to the database fail and the system is completely unresponsive to the point that I cannot even type any commands at the shell. I have seen this behavior in the past when the oninit processes use a lot of CPU resources, but it is usually pretty easy to track these down to some bad SQL/report writing. In this case, I'm trying to figure out what may be causing the system freezes. I have top and the dbtop utility from IIUG, but those don't refresh during or freezes. I am also unable to type any onstat commands until the system comes back. By that time, everything looks pretty normal with low load averages and our oninit processes at normal levels. I'm looking at the various system reports in OAT, but don't see anything that jumps out as the culprit. I'd appreciate any troubleshooting ideas.