Ok today I checked that my problem is definitely caused by the Win NT SP4. Since I did not read something similar on this list so far, it is possible that it only appears with the german version of the service pack. I don't know with which MSVC compiler version Zope's 17 .pyd files were built, but AFAI heard, service pack 2 for visual studio is fixes some problems SP1 creates mainly in conjunction with the lastest NT 'service pack', which is in fact a major OS change/ upgrade. Since our application is required to run on the SP4 machine (our customer believes it is, and it is advertised by M$ as the only solution to possible Y2K problems) my question is if someone has already built the .c files with the very latest compiler versions. If not (and they are not already) I'll do this myself, but it would save me a lot of time - please give me a short note. Maybe there are others on the list who have access to a german SP4 box and can confirm my expiriences so we could add this to the bug track list. Stefan