Link for Mobi2Mobi Tools windows compiled & Perl Version
I'm sorry guys, I've tried sussing out the problem with the newer AZW files from Amazon but I can't determine what the problem is exactly. I don't have a Kindle and I only purchase DRM free .mobi files so I can't really test the files you are having problems with. If you feel like doing some programming, you can grab the source code and do a debug while opening your file and see where it breaks in code. I'm guessing its something in the metadata which my parsing can't handle.