Python.exe has stopped working

Yesterday I successfully installed sip, pyqt4 and vtk (including python bindings) on a Windows 7 64bit VM.

However, when I do "import vtk", a dialog pops up saying "python.exe has stopped working".

Event Viewer shows that the error is related to sip, however "import sip" gives me no error

Log Name:      Application
Source:        Application Error 
Date:          3/19/2012 9:00:43 AM
Event ID:      1000
Task Category: (100)
Level:         Error
Keywords:      Classic
User:          N/A
Computer:      Virtual
Description:
Faulting application name: pythonw.exe, version: 0.0.0.0, time stamp: 0x4df4b9cc
Faulting module name: sip.pyd, version: 0.0.0.0, time stamp: 0x4f34f9ae
Exception code: 0xc0000005
Fault offset: 0x00004d96
Faulting process id: 0x810
Faulting application start time: 0x01cd05d025cac35c
Faulting application path: C:\Python27\pythonw.exe
Faulting module path: C:\Python27\lib\site-packages\sip.pyd

>>> import sip 
>>> sip.__file__
'C:\\Python27\\lib\\site-packages\\sip.pyd'