Hi, This combines two previous questions about problems I have been experiencing with large memory leaks and also lately zope being restarted regularly by a sigsegv(11) signal. Both of these issues have been "fixed" by running zope on our production server with a single thread. We are currently running zope 2.6.2, python 2.1.3, on debian stable. The memory leak problem could be reproduced on the dev server but the sigsegv problem could not be reproduced. Running the dev box single threaded did fix the leak problem there as well though. The dev box is due to be upgraded to zope 2.7 and python 2.3 but is there anything I should be looking at that could be the cause of these problems? I have done a lot of searching but have not found many clues to the next step other than upgrade zope. The page I read about running single threaded suggests a C extension being a likely cause. I have been reading up on creating c extensions for python, but how do you track down where/when existing python code makes use of a c extension? Being new to the debugging side of things, can someone give suggestions on links/info on simple explanations of debuggers and how best to use them to solve such an issue as I have here. Thanks for your help. Richard.