My DVD Player refuses to play MY discs but plays others

My Samsung 709 has stopped recognising and playing dvd-r's I've recorded on my Pioneer A104, no matter what type of media is used. It continues to play dvd-r's and +r's recorded on friends players. The discs continue to play perfectly on my Cyberhome 528 player and on both the A104 and my Asus E616 rom drive but my cousin says a disc I recorded for him last week refuses to play on his Sony player. I use either Nero 5.5.10 or Vob Instant CD/DVD to record with UDF disc and a setting of UDF 1.02 on both. I originally used Prassi Primo DVD, but it started screwing up my discs with the authoring all over the place. Am I suddenly doing something wrong or missing something, or could their be something wrong with my burner?

Create an .img file and burn that.

Using which soft?

DVD Decryptor