I do not know for sure what the problem is but I have a few ideas about what I would try:
1) remove the DRI section. It is useless and the docs tell you to, I doubt it makes a difference ... but its simple to do so why not.
2) Add a
line to the device section ... it stops just before reportng the video ram size (at least that is next in the working log file) so /maybe/ 4191 has some WeIrD issues with detecting ram size ... at least it can't hurt to try.
3) try other values for NvAGP ... in particular
might be interesting. It looks like the crash is a good ways before an of the AGP stuff, but its worth a try IMHO.
4) Option "NoDDC" "true"
The crash happens just before the ddc stuff so this /might/ help, but I doubt it, but again its worth a try.