I'm running on a Backtrack 4 Pre-Final hard drive install and upgraded to ubuntu 9.04

The only problem I'm having is when I run:
sslstrip -a -k -f
I recieve the following error:
Traceback (most recent call last):
File "/usr/bin/sslstrip", line 33, in <module>
from sslstrip.DataShuffler import DataShuffler
ImportError: No module named sslstrip.DataShuffler
Any thoughts?