Try the usual DVD lens cleaner then check Samsung web site for firmware updates.
We have had our Samsung HT-Q70 since it was brand new, and have not had any problems until recently. The last few movies that we purchased from a retail store (one example is "The Hobbit") will not load. One loaded to the menu, and froze in that spot. Another loaded, and started the movie, but every few minutes would stop, then start back up. After a few times of this happening, it would stop all together. If we put in any older movies (some just months old,) they would play without any problems.
We put the discs in an 3-4 year old GPC (Wally-World Special) and they seem to play fine. It there an update that I need (I found nothing on the Samsung website,) or does it sound as if my unit is too far outdated. We love the unit, as it plays all of the other discs fine, and are very happy with the sound quality for the area it is in.
Thanks for your time.