Specifically the section Anvil and MCRegion files found
Your region folder contains both .MCA (New 1.2 Anvil Format) and .MCR (Pre 1.2 MCRegion format) files. You only need one set of these region files. If you've updated your world to 1.2, then you probably need to delete the .MCR files. Be careful though. I am not responsible if you delete your world by accident. Please adjust your archive and re-upload your world.