I got a mail from a guy called "Goblin" and this is what he wrote: Just to inform u that 27.xx have some issues regarding playback of DVDs. Like, there's no subtitles, and the picture looks like lego blocks at a lowest bitrate.
This happened to me in PowerDVD XP, and 3.0 under Windows XP.
Under 23.11 from Nvidia things work just fine. *UPDATE* I got a mail from Kris Carruthers (NVmax Editor) and this is what he wrote:
Many people have this problem. Its hardware acceleration. If you have a fast enough PC then disable Hardware Acceleration in PowerDVD and all will be fine. These are beta drivers and this isn't really worth mentioning since a new set should be right around the corner and will most likely have the Hardware Acceleration fixed. Could this fix the problem? Here @ Warp2Search we have the latest patches for PowerDVD & PowerDVD XP, click on Read More for more info & direct links.

Personally, I use Detonator 27.42 and PowerDVD XP Deluxe (Build 1228) and I have no problems (me just lucky?).
Or does more people have these problems? For PowerDVD 3.0 Patch Build 0905 click here. For PowerDVD XP 4.0 Patch 1228 click here.