Whenever I use Ubuntu tweak's janitor to clear caches and I select all the files I want to delete and click "clean" nothing happens. (See the screenshot below) This has only began since I upgraded from 12.10 to 13.04.
As Donarsson pointed out in his comment, I think you just need to update. Ubuntu Tweak works fine for me in 13.04.
In a terminal, type these commands: