Remote desktop not working on mountain lion

My ARD does not work on Mountain Lion. The software opens but all I get is the menu at the top, and my only working option is to quit. I spoke to Apple support and they suggest (as they usually do) to reinstall the whole operating system, but I can't accept this as a valid answer as everything else works. There must be a way to fix this without having to reinstall a machine that came originally with Mountain Lion!