I'm running Mountain Lion on a MacBook and I use a Ubuntu server as my Time Machine drive. It works well and has done for a few months. I've upgraded to Mountain Lion via the dev program and I'm experiencing some issues with Time Machine that were not there before. I'm just curious whether anyone else is having these issues too. Sometimes, probably half the time, after waking the Mac from sleep, Time Machine complains that the disk is cannot be found. I can force it to check again and it still cannot see it. Selecting the disk manually prompts the 'do you want to change disk' dialogue box, even when selecting the disk that I usually use. Rebooting the Mac or sometimes reconnecting to the shared drive using Finder works and all is well again. It's all a bit weird. Yes I know this is early software, like I say, I'm just curious as to whether anyone else is having a similar thing happen.