Hi guys!

My Setup:
Distro: Slackware 11
X Server version: 6.9
Video Card: Nvidia Geforce FX 5900 (128Mb)
Direct Rendering: yes
Windows Manager: xfce-
Dual-monitors: yes

My problem:
When i resize my windows, say a firefox window, that doesn't happen very smoothly. Instead i can
see traces of the window frame following the window i'm resizing. When i do resizing a bit faster, it gets even worse - big chunks of that window stay on the screen but then disappear after a second or less.

Screenshot: http://isecuritylab.co.uk/scrfire.jpg

What do you guys think might be the problem here? and any suggestions on how to solve it?