I've been able to use DVD Decrypter to decrypt movie files to my external disk drive, and Nero Recode 2 to burn them to DVD using my Toshiba 16 speed dual layer burner. Most of the time everything has worked great except a few coasters here and there.

Recently I upgraded my PC to 2 gigs of RAM and a 7800 geforce video card.

After this upgrade I have started running into problems and I'm not sure where the problem is: is it in the software, the drives, where?

The problem manifests like this:
I no longer get a good decrypt. Even when I tell nero showtime to play the movie from the file, I see a lot of little specks and lines across the screen that mess it up. When I try to use Nero Recode, I get an error that a VOBU address is out of bounds.

Here is what I have tried to do:
I have first tried downloading and trying to decrypt using other programs. I tried using AnyDVD and RipIt4Me (which got me using DVD Shrink 3.2, the existing latest version of DVD Decrypter, as well as FixVTS1) and neither of these have worked. AnyDVD produces a bad decrypt as well and Nero Recode won't accept it, and RipIt4Me isn't doing it either; the burn is simply unreadable and my drives lock up my computer when I put the DVD in them.

Today I have used a laptop and its DVD drive to decrypt to the external drive using the latest DVD Decrypter. The decrypt looks good (plays in nero showtime), and Nero Recode seems to like it and burns it without complaint. However, it's a coaster, as the drives will not read it and the screen locks up as long as the dvd is in the drive. I've tried burning it slowly, doing the advanced analysis, anything I could think of. The DVD also isn't playing in any other drives (the laptop's or my regular dvd player hooked up to my TV).

Any pointers or troubleshooting ideas welcome!

Try checking the memory/RAM using memtest.