intel driver on a 82Q35 gets slow as soon as I rotate on a 1920x1200/1600x1200 display

[Thomas Glanzmann]

Hello,
I have a Intel 82Q35 connected via DVI to a 1920x1200 display. I run Debian
Lenny on the box. The acceleration is fine as long as I don't rotate the
display. As soon as I rotate the display the acceleration drops. Changing
between two virtual desktops is slow and ,,ls'' in a fullscreen xterm is also
very slow. Does anybody has an idea how to improve the behaviour? The same
happens with a resolution off 1600x1200. On my mac mini I'm able to have
1920x1200 display rotated running. But I have to start two Xserver in a serial
fashion, one so set the modes in the video bios and one to the actually work.

lspci output, Xorg.0.log, xorg.conf:

http://wwwcip.informatik.uni-erlangen.de/~sithglan/82Q35/

        Thomas