My computer is only 2ghz processor with 512mb ram and it works fine.
Yours is faster.
The only time I noticed when my monitor had the same symtons like yours have is when my computer ran without my graphics card. Once I loaded the drivers for the graphics card and go the card back on, the slow screen problems disappeared.
I'd say something to do with your video card.
If you cant fix it go buy a grpahics card and install it. If the problem disappears, then it was your video card.
If the problem still persists, return the graphics card and get your money back. That way you used the graphics card just for your testing purposes...lol...
Cheers,
Roy