Yes it does happen because it has happened to me as well, last night to be exact. While watching TV all of a sudden the screen saver pops on. Hitting any key brings the picture back. Obviously this behavior is a bug and needs to be addressed.
Well the problem was gone for awhile. Now it is back with a twist - now while watching a recorded program the receiver turned channels on me. THe remote was 10 foot away form anyone so it was not accidentially hit. Hmmm....