Your experiencing the files /usr/X11/lib/modules/libwfb.so and /usr/X11/lib/modules/amd64/libwfb.so being clobbered (overwritten) with an incompatible version. This is due to the Xorg being upgraded to v1.5. Nvidia's install utility didn't become aware of the different versions of Xorg's at that time. The simple fix would be to replace the clobbered files. I've conveniently placed them on my website for download (the alternative would be to search the snv disk for it, I don't know what package the files are in).
Please be sure to place the appropriate file in the correct location, as the 32 bit and 64 bit versions have the same name.