[PyMOL] cannot find _cmd module

Hello,

Eh, I think this is a rather basic question. So I built PyMOL on Win32, tried
to run pymol.bat, which calls python $PYMOL_PATH/modules/pymol/__init__.py,
which complained:

Traceback (most recent call last):
  File "D:\thli\root\misc\pymol-0.90\modules\pymol\__init__.py", line 92, in ?
    import pymol
  File "D:\thli\root\misc\pymol-0.90\modules\pymol\__init__.py", line 300, in
?
    import _cmd
ImportError: No module named _cmd

I have PYTHONPATH set to $PYMOL_PATH/modules. Is it something obvious I'm
missing?

Thanks much!

Tina