nv driver and screen corruption

[Sad Clouds <cryintothebluesky%googlemail.com@localhost>]

Hi, I'm using NetBSD 5.1_RC3, Xorg is using nv driver with NVIDIA GeForce4 MX 
440 graphics card.

For quite some time now I have been seeing screen corruption, this usually 
happens when Firefox is running. I'm not sure if Firefox causes it, or buggy 
nv driver.

What I mean by screen corruption is this - bands of vertical stripy lines that 
corrupt text and graphics on the screen. This happens quite randomly when for 
example, scrolling text in Firefox or switching virtual desktops.

Has anyone seen this and maybe knows what is going on?