Problems watching video with the Radeon HD 3850

[Aniruddha]

First of all I must say I'm impressed by the latest stable freebsd 
release (7.1). A lot of hardware which didn't  work before now works out 
of the box :)  I only have problems watching video, it feels sluggish 
and there frequently runs a stripe through my screen. Which settings 
(and driver) do I need to use in order solve this? I now use the 
radeonhd driver. I have a  Radeon HD 3850 (RV670PRO) card . Thanks in 
advance!

Regards,

Aniruddha