Help Desperately needed!!Pioneer106S:some DVDs not playing (

[PepsMax]

Hi!! I would be very thankful if anyone can help me out with that problem.
When I borrow DVDs from a shop which are clean at all and not damaged, many of them aren't playing on PowerDVD.It says that it cannot play it back because it might be damaged or dirty.But it is NOT!
When I open the DVD in smartripper it says untitled DVD but checks the vob files and says OK.Then when I try to rip, it cannot find a key for the files(searches long but then gives up)..

And now the curious thing:
When I open vob files in FlaskMPEG I can view the whole video!!
Why's that?Maybe wrong region code or what?
Thank you very very much for helping me!

[Sefy]

Have you changed your DVD's Firmware ? i'm using the same drive and a hacked firmware and I have no problems so far.