ActionClass error

[Jerry]

Vizard 2.5g gives this error when any script is run:

** ERROR: Failed to initialize python
Traceback (most recent call last):
File "<string>", line 1, in ?
File "C:\Program Files\Vizard25\viz.py", line 16, in ?
import new
File "C:\Program Files\Vizard25\bin\lib\new.py", line 16, in ?
except ImportError:
File "C:\Program Files\Vizard25\sid.py", line 10, in ?
from vizact import _paramlist_
File "C:\Program Files\Vizard25\vizact.py", line 271, in ?
class VizGotoAction(viz.ActionClass):
AttributeError: 'module' object has no attribute 'ActionClass'

This happens even if you just do

import viz
viz.go()

How can I fix this?