I updated bunch of packages today (linux-amd-staging,mesa etc) and now DVI-I-1
is not recognized but it is shown as DVI-D-1. This also brought new problem:
monitors 'blink' randomly, about every ten seconds and it is VERY annoying. 

I also left the computer for few hours monitor powered off, and then when I
came back and it should've shown lockscreen monitor repeatedly showed "signal
not found" and then got it, and lost it immediately again. I couldn't get
picture to either monitor but Ctrl-Alt-Del restart did work.