I have a Samsung DVD-V4600. It worked fine until yesterday. I tried a DVD-R in it, and it played the movie fine, however now it won't play regular DVD's. It keeps saying "the disk cannot be played; check disk". It will still play the DVD-R I played the other day. I don't know anything about region codes or locks or hacks or anything like that. Could I have messed something up? Can it be easily fixed?