I should have access to a 64-bit windows environment tonight and will try to replicate all of this there. However, as I say, the build runs, so the environment (if properly installed) should run.
Just installed a clean 64-bit Windows 7 Enterprise machine. Installed the following files in order:
* python-2.7.3.msi * pygtk-all-in-one-2.24.2.win32-py2.7.msi * libxml2-python-2.7.7.win32-py2.7.exe * pywin32-218.win32-py2.7.exe * pyserial-2.5.win32.exe
Downloaded the chirp code, and ran the installed Python on chirpw. It started up perfectly the first time. Hopefully checking your downloads against the list above will help identify the problem.
I'll keep this VM image around for a bit in case there are questions, but it creeps me out having two Windows boxes (even if they're VMs) in the house :D