No way that I know of other than manually if you've already committed the actions you want to change. But there's a fantastic script for being able to restore them if you run it *before* making the changes.
http://www.linuxquestions.org/questi...threadid=91333
So, yeah - pretty much a manual task of hoping you get it right this time, I'm afraid. But better luck next time.
Basically, though, no one but root should have write access to /usr. Directories, executables, some libraries - I dunno - that stuff should be executable. Most everything else in /usr can be world readable (I think).