We run a MacMini (about 1.5 years old), Keynote, a 17" monitor at the projection station, the other video feed from the mini goes to a projector mounted to the ceiling. Video out to projector is RCA composite video. We run the composite video because this was installed almost 10 years ago, running Powerpoint on an old G4 Mac.
In all those years, with the G4 & the Mini, I've never had it lock up.
Most videos I play with Quicktime 7 player, using the "Present Movie" command. They play on the big screen & when they finish, it goes back to the Cross background that we use.
Fred