https://bugzilla.kernel.org/show_bug.cgi?id=79011
--- Comment #14 from Thue Kristensen thuejk@gmail.com --- I have the same problem, and turning the screen off and on doesn't work. The computer is completely frozen. (sysrq-boot does work)
Rarely when changing resolution (like during boot), the screen says "signal out of range", but turning the screen off and on does help then. I believe that is a separate bug.