OK. I checked the nVidia driver code and it seems that it failes to load symbols from the AGPGART.
I recompiled the AGPGART into the kernel... but still no go.
agpgart: Found an AGP 2.0 compliant device at 0000:00:00.0.
agpgart: Putting AGP V2 device at 0000:00:00.0 into 4x mode
agpgart: Putting AGP V2 device at 0000:01:05.0 into 4x mode
0: NVRM: couldn't find pre-allocated memory!