Just installed Crimson 16.12.2 and get black screen at windows login (no cursor, nothing). After looking on the web etc, and trying different setups, it appears that it's caused by display port and HDMI thjat are connected together.
I've got a 390 and use 4 monitors (2 on dvi, one HDMI and one on display port).
Trying to disconnect the diplay port or HDMI (or just not power the display on when rebooting) before restarting make the problem disappear.
PLEASE FIX IT !!!