Have you tried the version from the other thread?
Pandora Radio For Xbmc4xbox Branch(fork), Pandora Radio Python Script.I have tried it and I can't get it working myself but I think I found something a bit ago saying that some plugins don't work with the latest stable release, which is what I am using, they need a newer version.
Not sure what I can link to here but just google xbmc svn.
I'll post back if I find something that works.