The cvs2svn test suite, which runs reliably under Linux + Python 2.4/2.5 + Subversion 1.5, fails when run under psyco:
$ svn checkout http://cvs2svn.tigris.org/svn/cvs2svn/trunk cvs2svn --username guest
$ cd cvs2svn
# Add lines to cvs2svn script to fire up psyco
# Test 77 is a simple test from our test suite that fails:
$ ./run-tests.py 77
cvs2svn_lib.common.InternalError: ID changed from 2 -> 3 for Trunk, r2
cvs2svn uses lots of temporary files, many of which contain pickled data. The contents of the files are different between runs with and without psyco, making me suspect (though without any confidence) that the problem might be related to pickling. I tried using the pickle module instead of cPickle but that didn't help.
If I turn on PSYCO_DEBUG = 1 and HEAVY_MEM_CHECK = 1, then the program aborts with:
python: c/linuxmemchk.c:30: _na_find: Assertion `_na_start+4096 <= data && data < _na_start+4096*16384-4096' failed.
If there is more info that I can give you to help you diagnose this, please let me know.