Sorry, if i havent been clear.
The Plextor is in my HTPC.
The LiteOn is on my main PC.
The DVD in question has problems on the HTPC, im using Media Portal and WMP.
Media Portal freezes completely, WMP seems to play without stopping but from the drive noise its clear that everything is not okay.
There are no problems with playback on my main PC.
Ive had similar things happen with other DVD's(also some new original DVD's, though they only froze temporarily) and its really annoying me as my HTPC is what i use for all my DVD playback.
I did the transfer speed test on the Plextor because thats the drive that causes the problem.
I have now tried running Nero's DVD Speed ScanDisc using the Plextor and it reported some bad sectors on the disc in question. When i run the exact same test on my main PC using the LiteOn problem everything is fine.