[Zope] Zope eating CPU/RAM - how do I find the culprit?

Our production Zope machine has developed a habit over Christmas where it starts eating CPU and RAM (one Python thread on 100% CPU time, and I've seen kernel messages indicating that Zope was killed because it hit an out-of-memory condition which means it sat on ~500Mb RAM). I'm completely in the dark about what causes this (probably some of my own code, I installed some new bits a couple of days ago), but what's worse: I really don't know how to set about finding the problematic code. Is there a way to find out what code a thread is running? -- Cees de Groot http://www.cdegroot.com <cg@cdegroot.com> GnuPG 1024D/E0989E8B 0016 F679 F38D 5946 4ECD 1986 F303 937F E098 9E8B