Comment 54 for bug 763052

Wow, so right on boot:

[ 15.639931] nouveau E[ DRM] GPU lockup - switching to software fbcon
[ 15.643599] [drm] Initialized nouveau 1.1.1 20120801 for 0000:04:00.0 on minor 0

It locks up before the probe is even done! One thing to check -- do you have any old firmware in /lib/firmware/nouveau? You shouldn't need any firmware to run nva3 (except the video firmware if you want vdpau).

Also, could you produce a log with

drm.debug=14 nouveau.debug=trace

That might provide more info as to what's going on.