Strange Problem reading DVD

Hi, I have this problem when reading a All-Region, Unencrypted DVD. My drive does not seem to read this disk. Keeps reading.. and hangs OS. I have a Samsung SD-612 DVD ROM. Running on AMD Duron 750MHz Windows 98SE. It happily reads Region 1 encrypted DVDs. Even SmartRipper, DVD Decrypter, PowerDVD cannot access this. On one occasion I was able to read the files (played back two Vobs using Mediafiles option of PowerDVD) and after shut down and restart back to the same problem. ASPICHK shows properly installed and functioning properly. Is this a problem with drive or DVD? Any workaround, tests? Thanks in advance Dinesh

What 'I/O Error' does DVD Decrypter give when you 'try' and read it?

Ok, so take the disc out of the drive and insert it once the program has loaded up properly. Better still, load dvd dec, enable I/O debug mode and THEN put the disc in the drive. Tell me whats being said in the log for the CDB: 00 00 00 00 00 00 - SENSE: XX XX bit I need to know what the XX XX says.