New to this Forume Site!

I have just built a new system with a Sony DVD RW DW-U18A drive in it. I have upgraded to Nero 6 and i have a querky problem. The drive and software work without error when a audio CD is loaded into the drive. I can preform a speed test (Within Nero) and play audio file with no problems but when i load a DVD into the drive i get problems. If i place a DVD movie into the drive it recognises that a DVD has been placed in the drive and it even changes the title within windows explorer but it cant play it. I start Nero Showtime 2 to view the movie and then it will not proceed any further. If i then try to do a speed test (within Nero) with the DVD loaded in the drive it returnes a error message ( I have written it down and if need be i will added it to the thread) stating that the sector is scrabled. Even within Media Player 10 it does not play the movie?? Has enyone else seen this problem where the drive will play audio CD but not DVD cd's. I must admit i have not tried any other DVD software as i would like to stay with the Nero Showtime software. I have also not tried to burn a DVD within nero since i though if the software wont even play a DVD then i wont try to burn one?
Thanks for any replies AZZY