mga display messed with kernel >2.6.22

[Daniel Tippmann]

Hi *,

I have a messy display since a Linux kernel upgrade (to 2.6.23, or 24, 
or 25). The screen (CRT) is very distorted and flickery, and sometimes 
just switches off because of illegal (low) VertRefresh rates.  In fact, 
it will not go higher than ~50 Hz unless I choose a low resolution (e.g. 
1024x768). The distortion is related to CPU usage (i.e. under higher CPU 
load, it gets better).

Everything is OK if I go back to 2.6.22.

I'm on Gentoo, Matrox G550, nForce2 AGP, xorg-server 1.3.0, mga 1.4.6.1. 
(also tested server 1.4.2 and mga 1.4.9). Nothing revealing in xorg.0.log.

Any hints highly appreciated!

Cheers
Daniel