We have a PIX 501 6.3(5) 50 user license that is rebooting itself several times per day, causing brief outages. Only 9 out of 50 licenses are in use, and memory use is about 75% (12385952/16777216). I've enabled debug logging to remote syslog, and all I see is normal use and then messages stating that the inside and outside interfaces changed state to up.
The PIX is sitting on a shelf on a rack in a server room, so I'm hesitant to believe it is a shaken loose power connection that is causing reboots.
Is there anything else I should be looking at?