Same problem, I am in the middle of editing and the marker goes straight back to start as soon as I strt to play the movie. Need help now as I am editing for a movie for friends.
Not sure which version you have of MEP, but try the following. Open the program and open Program Settings, which you will find under File. You should find the adjustment there. Check under Playback maybe??
de-installing was a bit of a long shot. If you can't import via firewire, then transfer directly to your computer and import via the browser in the Edit window. If any codecs need to be activated, the dialogue should appear automatically.
In program settings, under Playback, click on Space bar stops............... That will sort that one out for you.