Ati Sapphire 4870 and Corel Draw (2D)

[zombiehead]

I bought a new PC recently:

P2 940 BE
8GB Corsair DDR2 800
HD 4870 1 GB Sapphire Vapor
500 GB WD HDD
600 Watt CM PSU
Win XP 64

Now the problem: when I am using Corel Draw I usually move around the screen images and the movement of these images is very slow (each image 3-4 MB) and lags behid the movement of the mouse. What can cause this?
Thanks!