I wanted to use gnomenu with awn and had the same problem. I can't say that I know python as a programming language, but I am a developer and I was able to get it working. There might be a better way to solve the problem but this worked for me.
The attachment has two files that I modified:
rename those two files found in your [/usr/lib/gnomenu] folder to something like Menu_Items.py.old and MenuParser.py.old and then copy the two files I've attached into that folder.
The error message is identical to the one I was getting and has to do with the way the menu is being parsed. For some reason the first pass fails because there are no items in the menu or something like that. I put a check in place to avoid that error. I then ran into a couple issues with the search, but that should work too.