The subject pretty much says it all, but here are some more specifics: I have an iMac G5 with Tivo Desktop 1.9.3. It has worked fine in the past, but I tend to turn it off on occasion because it uses up a lot of processing power even when idle. When I tried to start it yesterday, it wouldn't. When I click the Start button, it just switches back from Stop to Start within one second. I have installed a few updates (iTunes 7.3.2, OS X 10.4.10) so I have no idea where the incompatibility is (if there is one).