DVD quality

poor dvd quality, 'blotchy screen'

Recently, for no aparrent reason, the quality of my picture when playing a dvd has deteriorated. The picture has small like squares when I go to full screen mode when watching. I have an asus laptop with an ATI mobility radeon 9100 graphics card, and also a pentium centrino processor.
PLEASE HELP!!!
Thanks.

Clarification

Just a few questions to clear up:
Does this happen with only specific DVDs?
Is your laptop plugged in when you watch the movie? (When a laptop is on battery power, the processor speed drops significantly.)
What DVD player program do you use?

Have you tried toggling any "Hardware Acceleration" feature in your DVD decoder? In WinDVD they are located in the Setup -> Video menu.
If that's the case a Driver or program update ought to solve the problem.

I use cliprex dvd player although I dont actually like it, it happens with every dvd I watch.
The picture looks likes lots of little squares and it doesn't have the crisp texture of a television, like it used to. I have the latest video drivers for my card as well.
The laptop is also plugged into the mains to answer your question.