> Hmm you should have a file in the temp folder called lib/Crypto/Util/number.pyo
> It would be interesting to see Util.__file__

The temp folder gets immediately deleted before I can see the contents.

To try and get the chance to see what happens, I have pulled lp:wubi
and built wubizip on a separate machine.

Results on the thinkpad:
---------------------------------

C:\u-904\wubi>python.exe main.py --verbose
'import site' failed; use -v for traceback
Traceback (most recent call last):
  File "main.py", line 23, in ?
    from wubi.application import Wubi
  File "C:\u-904\wubi\lib\wubi\application.py", line 26, in ?
    from wubi.backends.win32 import WindowsBackend
  File "C:\u-904\wubi\lib\wubi\backends\win32\__init__.py", line 1, in ?
    from backend import WindowsBackend
  File "C:\u-904\wubi\lib\wubi\backends\win32\backend.py", line 33, in ?
    from wubi.backends.common.backend import Backend
  File "C:\u-904\wubi\lib\wubi\backends\common\__init__.py", line 1, in ?
    from backend import Backend
  File "C:\u-904\wubi\lib\wubi\backends\common\backend.py", line 42, in ?
    from signature import verify_gpg_signature
  File "C:\u-904\wubi\lib\wubi\backends\common\signature.py", line 29, in ?
    from openpgp.sap.api import verify_str
  File "C:\u-904\wubi\lib\openpgp\sap\api.py", line 49, in ?
    import openpgp.sap.crypto as CRYPT
  File "C:\u-904\wubi\lib\openpgp\sap\crypto.py", line 47, in ?
    import Crypto.Util.number as NUM
  File "C:\u-904\wubi\lib\openpgp\sap\crypto.py", line 47, in ?
    import Crypto.Util.number as NUM
ImportError: No module named Util.number

C:\u-904\wubi>python.exe -v
# installing zipimport hook
import zipimport # builtin
# installed zipimport hook
'import site' failed; traceback:
ImportError: No module named site
# C:\u-904\wubi\lib\warnings.pyc matches C:\u-904\wubi\lib\warnings.py
import warnings # precompiled from C:\u-904\wubi\lib\warnings.pyc
# C:\u-904\wubi\lib\types.pyc matches C:\u-904\wubi\lib\types.py
import types # precompiled from C:\u-904\wubi\lib\types.pyc
# C:\u-904\wubi\lib\linecache.pyc matches C:\u-904\wubi\lib\linecache.py
import linecache # precompiled from C:\u-904\wubi\lib\linecache.pyc
# C:\u-904\wubi\lib\os.pyc matches C:\u-904\wubi\lib\os.py
import os # precompiled from C:\u-904\wubi\lib\os.pyc
import nt # builtin
# C:\u-904\wubi\lib\ntpath.pyc matches C:\u-904\wubi\lib\ntpath.py
import ntpath # precompiled from C:\u-904\wubi\lib\ntpath.pyc
# C:\u-904\wubi\lib\stat.pyc matches C:\u-904\wubi\lib\stat.py
import stat # precompiled from C:\u-904\wubi\lib\stat.pyc
# C:\u-904\wubi\lib\UserDict.pyc matches C:\u-904\wubi\lib\UserDict.py
import UserDict # precompiled from C:\u-904\wubi\lib\UserDict.pyc
# C:\u-904\wubi\lib\copy_reg.pyc matches C:\u-904\wubi\lib\copy_reg.py
import copy_reg # precompiled from C:\u-904\wubi\lib\copy_reg.pyc
Python 2.3.5 (#62, Feb  8 2005, 16:23:02) [MSC v.1200 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> ^Z

# clear __builtin__._
# clear sys.path
# clear sys.argv
# clear sys.ps1
# clear sys.ps2
# clear sys.exitfunc
# clear sys.exc_type
# clear sys.exc_value
# clear sys.exc_traceback
# clear sys.last_type
# clear sys.last_value
# clear sys.last_traceback
# clear sys.path_hooks
# clear sys.path_importer_cache
# clear sys.meta_path
# restore sys.stdin
# restore sys.stdout
# restore sys.stderr
# cleanup __main__
# cleanup[1] zipimport
# cleanup[1] warnings
# cleanup[1] nt
# cleanup[1] signal
# cleanup[1] linecache
# cleanup[1] exceptions
# cleanup[1] types
# cleanup[2] stat
# cleanup[2] copy_reg
# cleanup[2] UserDict
# cleanup[2] ntpath
# cleanup[2] os.path
# cleanup[2] os
# cleanup sys
# cleanup __builtin__
# cleanup ints: 4 unfreed ints in 1 out of 2 blocks
# cleanup floats

C:\u-904\wubi>

-----

What would you like me to try next, if anything?

I have never used python, so you'll have to explain slowly :-)