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Just fyi, in case anyone else encountering something similar:
On my setup (Thinkpad T510, i915 graphics) one of the relatively recent 4.5 kernel upgrades (not sure which one, unfortunately) introduced problems related to VT switching while Xorg server is running: Switching between VTs when Xorg was not running was fine, but if Xorg was running in one of the VTs, attempting to switch between VTs (either via chvt or <ctrl><alt>Fn) would frequently result in complete loss of video (black screen, occasional "twinkling" near the edges) with no obvious way to restore normal video. System was not frozen per se (still possible to slogin in and behavior was normal) but video was completely hosed.
For me, downgrading to 4.4.5-1 completely solved this issue: Switching VTs via chvt or <ctrl><alt>Fn is entirely stable now.
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