384 driver won't let X start in ubuntu 17.04

The machine is a Thinkpad p50.It is in discrete graphics mode with two external monitors attached.
It works with 375 and 381. The latest beta has been packaged and I tried it.
I can not proceed past the login screen. It’s gnome desktop with gdm.

nvidia-bug-report.log.gz (160 KB)

It’s a crash in libmutter

ul 18 09:09:24 raffles kernel: [ 34.461705] gnome-shell[4524]: segfault at 28 ip 00007fe2c0f34d74 sp 00007ffd8e2761d0 error 4 in libmutter-0.so.0.0.0[7fe2c0eed000+131000]
Jul 18 09:09:24 raffles gnome-session[4395]: gnome-session-binary[4395]: WARNING: Application ‘org.gnome.Shell.desktop’ killed by signal 11
Jul 18 09:09:24 raffles gnome-session-binary[4395]: WARNING: Application ‘org.gnome.Shell.desktop’ killed by signal 11
Jul 18 09:09:24 raffles kernel: [ 34.685808] gnome-shell[4533]: segfault at 28 ip 00007feb32769d74 sp 00007ffc8582c000 error 4 in libmutter-0.so.0.0.0[7feb32722000+131000]
Jul 18 09:09:24 raffles gnome-session[4395]: gnome-session-binary[4395]: WARNING: Application ‘org.gnome.Shell.desktop’ killed by signal 11
Jul 18 09:09:24 raffles gnome-session[4395]: gnome-session-binary[4395]: WARNING: App ‘org.gnome.Shell.desktop’ respawning too quickly
Jul 18 09:09:24 raffles gnome-session-binary[4395]: WARNING: Application ‘org.gnome.Shell.desktop’ killed by signal 11
Jul 18 09:09:24 raffles gnome-session-binary[4395]: Unrecoverable failure in required component org.gnome.Shell.desktop
Jul 18 09:09:24 raffles gnome-session[4395]: gnome-session-binary[4395]: CRITICAL: We failed, but the fail whale is dead. Sorry…
Jul 18 09:09:24 raffles gnome-session-binary[4395]: WARNING: App ‘org.gnome.Shell.desktop’ respawning too quickly
Jul 18 09:09:24 raffles gnome-session-binary[4395]: CRITICAL: We failed, but the fail whale is dead. Sorry…

Purge and reinstall of gdm3 fixed it.