If you are viewing the commit info of a commit that contains a file not in your "current" head, you get a "Invalid path info" error. The attached (simple) patch seems to fix it, but I'm not sure if that's the "right" way to do it, it builds the same URL as when you use the tree to find that file. Also when you do view that file, you get this at the top:
Last commit for FILENAME:
I'm guessing a similar minor problem is causing that.