Vista - Issues with Radeon 4850(8.12) & Vista x64

Hey All -

First time poster, long time stalker.

I just put together a new system, and everything is running swimmingly except for 2 things:

1) When i boot into vista, and there is that "transition" into the login screen, there is sometimes artifacting on the transition (I.E. black blocks in random patterns on the screen). Is this a normal occurrence on load? or?

2) When i play DVD's using WMP (and the default MS Codec that comes with Vista Ultimate) i will randomly get "Slow Downs" or "Dropped Frames" which although not affecting the audio, proves very distracting. This does not happen when i use VLC.

Anyway, any and all help/advice/etc... would be greatly appreciated!

e8400
Gigabyte EP45-UD3P
Sapphire 4850
4GB G.Skill PI Black ram (DDR2-800)