I still use DP. I just turn on my monitor as soon as I start my PC (or at least before Windows starts). No issues then. If you forget, however, you get to rearrange all your icons again.
I believe this may be HP's issue. Old firmware or w/e. But I haven't contacted them because I bought the monitor abroad, so RMA would take forever.
I was also trying to find a more recent BIOS for my 6970, but the reference cards all have the same version. Couldn't find anything more recent...
Anyway, if someone finds a solution or workaround, please post it here.