I had a segfault too with latest xorg-server and nvidia-190.42.
On the Arch Linux BBS, jxy found that it was related to the "TwinViewXineramaInfoOrder" option : http://bbs.archlinux.org/viewtopic.p...648490#p648490
I first commented this line, and it worked. Now I have changed it from "DFP, CRT, TV" to just "DFP", and it works too.
Since everything worked fine with the 185.36 driver, this is probably a regression in the 190.42 driver...