I had the same problem, in my case the PyQt4 library was missing. You can install PyQt4 by downloading the appropriate installer from the Binary Packages section on PyQt4 Riverbank .
How I investigated the problem
When I installed git-cola in the default directory and tried to start it using the command line
C:\Program Files (x86)\git-cola\bin>python git-cola.pyw
I got
Sorry, you do not seem to have PyQt4 installed. Please install it before using git-cola. eg: sudo apt-get install python-qt4
Note
I have two Python 2.7 installations, one in c:\program\Python27 , and the other in C:\Users\UserName\Anaconda2 , I used the first. I also installed Python SIP a while ago, I'm not sure if this is required by git-cola.
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