I think that mental bugs happen much more often in a "jam" situation that when you haven't practiced with the group you will be playing with. 5 or 10 minutes of playing is not enough to get comfortable with other players and get the feel for the speed and the order that you'll be asked to play in.
If you practice for a few hours during the week with the same group, I'd bet your mental bug rate would drop like a stone.
Dave prepares us for the worst case jam situation where you sometimes don't know the song until the last minute and you may have new players all around you. A good skill to have but you pay a price by blowing solos, playing in the wrong key, and even blanking out completely.
