I am experiencing the same behaviour both with VGA and HDMI. The only difference is that my system freezes few seconds after switching to tty1.
My /var/log/messages displays this two lines right before the freeze: Mar 18 12:06:38 kernel: [11136.909382] traps: gnome-shell[2859] trap int3 ip:7f9d31adb87b sp:7ffe42e5e8f0 error:0 Mar 18 12:06:42 kernel: [11140.123641] gnome-shell[4195]: segfault at 272bc2d290 ip 00007fde5b4384fc sp 00007ffe88e3a4c0 error 4 in libmutter.so.0.0.0[7fde5b3b2000+fc000] Thanks.
