xorg-7.0 with nv/nvidia driver: random screen flashing

[Bram]

Hi,

I'm using xorg-7.0 on kubuntu with either the nv or nvidia driver. With
either driver, at seemingly random intervals, the screen flickers very
shortly. 

It's hard to describe this flickering. It occurs irregularly. Sometimes
it doesn't happen for 10-20 seconds. Sometimes it happens 5 seconds in a
row. When it happens, it appears that another image is shortly displayed
for about 1/25th of a second. This 'other image' is not random data, it
looks like a part of the video memory, perhaps displayed at the wrong offset.

This phenomenon occurs both with the nv and the nvidia drivers. It does
not happen with the vesa driver. Also, I had to set HWCursor to false,
otherwise the (usb) mouse wouldn't work.

Strangely, these problems only started to occur after I switched from
debian amd64 testing (with xorg-6.9) to x86 kubuntu (with xorg-7.0).
Before the switch, I used the nvidia driver and things worked flawlessly.

The video card is an integrated geforce on an nforce4 chipset:

0000:00:05.0 VGA compatible controller: nVidia Corporation C51 PCI
Express Bridge (rev a2)

The xorg server used:

X Window System Version 7.0.0
Release Date: 21 December 2005
X Protocol Version 11, Revision 0, Release 7.0
Build Operating System:Linux 2.6.15.7 i686
Current Operating System: Linux pcbram 2.6.17.13 #4 SMP PREEMPT Thu Oct
19 10:57:49 CEST 2006 i686
Build Date: 16 March 2006

Any clue on what may be the source of this problem? I've searched the
bugtracker & mailing lists, but couldn't find anything appropriate.

Bram