I upgraded to X2 with the early preorder folks, and the first time i installed i had the same issue. I reinstalled everything and it seemed to fix it but now it's back and I do not want to have to reinstall the program every time this happens. I run an i7 with 12gb of ram, windows 7, and actually run sonar on a different user profile than my everyday workflow to isolate it as much as possible (in response to past driver conflicts). More details: Once i open a project, i can work one it for a bit but it'll always be when i'm mixing something during playback that once i stop playback, everything locks up, after 10 or so seconds the screen will turn that light grey, and then i exit and "close program" rather than "wait to respond" (it never will). This is all annoying, but the biggest issue is that to reopen Sonar at all, I have to restart my system. I can start the task manager and find a Sonar.exe running but the process refuses to end (actually sometimes i can wait it out but it takes a bit). I hope someone out there can help me... X2 is brilliant otherwise.