I have checked several ways.. identical machines, identical files, settings etc.. fire both.. the ML machine will be very very far behind in a short bit of time.. I have been a heavy catalyst user for years and all the settings that you would check are the same and as they should be. This came up when I was transferring a clients show from a machine rented from myself to one I built for them. The newer machine will only run ML, new macbook pro yada yada. When I was testing the system before delivering to client I noticed that when freerun the new machine would not match the song it was programmed too. This was never an issue with any machine I used running SL. I checked everything, I checked several types of machines all with exact same results. When I test with an older macpro I can run a song from the show freerun in SL and it tracks perfectly as it was created to.. take the same machine on ML... falls behind quickly. Its is really quite strange. All playmodes are the same result save for audio playmodes as the audio playback "locks" the machine into playing at the correct speed. That was my fix for that particular show as all of the video files had a timecode audio track that we weren't using. Simply by changing my playmode to audio everything lines up perfectly. I have checked the global playback rate, play speed, etc etc etc. Any thoughts? I would bet you can duplicate this issue. Even My 6 year old macbook will track perfectly when running this show.... As I said.. quite interesting. I would value your input. Also.. with HUD up there are fun artifacts and tearing quite often. Gui also renders incorrectly on every machine I have tried ML on.