I broke my X

[Norval Watson <norv@longforest.com>]

Hi,
My xserver is broken, maybe because I was a bit late changing my sources from
debian-pure64 to debian-amd64 to just debian. I also did apt-get -f install a
few times which might have made it worse.

/var/log/Xorg.0.log shows
...
Failed to load module "GLcore"
...
Failed to load module "speedo"
...
Failed to load module "nv"
...
Failed to load module "mouse"
...
Fatal server error
no screens found

I am running kernel 2.6.16-1-amd64-k8

What might I try to rectify this situation?

Thanks
Norv