I've isolated the problem, it seems the DisplayPort does not get initialized. Have no other OS to test this behaviour, not a replacement GPU card. However i really doubt the displayport just "died" on me, neither is the error caused by hardware failure of the screen itself.
Admitted, it's a luxury problem (i cna still work with 2 display's connected to the DVI ports), but it used to work fine with 3, now it's all fubar, and X is tripping. Maybe that helps. If you need any additional info, i'm happy to provide it.
