We have had a similar experience with ML and FCP7. We upgraded about a month ago to 10.8, everything was working smoothly, then unexpectedly, Final Cut would halt on startup. It would get to the point where it was profiling for RT, then simply disappear. There is nothing in the crash logs, it just disappears on startup. We tried using some cleanup utilities to remove all of the Apple ProApps from the system and reinstalling FCP7, and the same thing happened. Then a clean install of 10.8 and a clean install of FCP7; same problem. Today we’re retrograding the workstation back to 10.7 and plan to keep it there until the end of time, or at least until our editorial staff is up to speed on Smoke. We’re not the only people on the interwebs who are having this problem.