[Zope] Zope stalls indefinitely

Thought we had a problem of ours fixed, but here it is once again, a month later. Zope, every once in a while, will just stall indefinitely. The Zope process doesn't die, it just hangs. Everything was fine for a month or so, and now the problem's started again, about every hour. We're running 2.1.6 on Solaris with pgsql and the ZPyGre adapter and the most recent copy of FSSession. Any thoughts. I've posed this question to a lot of people many times. Now that it's back, I'm hoping for fresh insight.