[Zope] Problems with memory leaks

I've been using Zope 2.5 for some months now basically for thermodynamic calculations, and I have discovered memory leaks. I've installed 10 extensions where 4 of them are accessing C++ code (with no leaks), and the 6 others are using MySQL to get some data. When I'm using XML-RPC from the client to access the functions I can see that the memory is eaten on the server. How it it possible for Zope to leak memory?? When I'm cheking the memory it seems like the memory is constant for some time, but suddenly jumps up a few kb. Is this normal? Could it be that the garbage collector is not doing his job? PS. I'm not using any global variables which I write to. Greetings from, Geir Arne Evjen Norway