Man, I see you got some HP monitor, mine is HP LP2475w and problems with DisplayPort appeares even in my old AMD/Gigabyte rig even with HD4870, now with Intel/Asrock and HD6850/Integrated GPU is all the same. So I think that it's not only DP problem but HP+DP. In my case it's not blank out of picture but rather lack of initialisation of picture after boot, if you got more than 1 display connected to your pc (I got 3 sometimes) then even worse for you.