To whom it may concern:

System Debian wheezy, laptop.

Symptom After an kernel upgrade to 2.6.39, console dimension got wrong, (maybe 800x600 at the center of the screen) and X fails to kick in complaining that dri device is missing.

Solution Disable rivafb (kernel option)

I think nouveau driver used to depend on rivafb, if I remember correct....

As some other thread says, I had some trouble installing nvidia driver. For my purpose, nouveau is good enough.

Closing remark Happy Penguins!

Correct. It seems like you cannot use dri with the Nvidia proprietary drivers. DRI (Direct Rendering Infrastructure) is for making fast open gl implementations by directly accessing video hardware. This provides hardware acceleration for graphics drivers. <-- This is just my take on summarizing what I found at http://dri.freedesktop.org/wiki/; meaning I just suppose Nvidia has their own framework for accessing the hardware with their drivers.

FYI, last time I looked (a couple weeks ago), Nouveau was still experimental; they recommend Nvidia drivers for any 3D or fluid graphics.