I'm running Direct x V11 on my windows 7 with no problems, I believe it was for anything before v10.
Was you running with BA enabled ? There are some other people who have had similar problems and we think now it may be having BA enabled.
Try your next session with it off. If you find you don't get the same problem then it might help narrow down this problem.
This thread has more on this:
http://forum.mtu.com/showthread.php?t=12173
What I have noticed is that you and Kod from the other thread are both running Dell 1545 models, could there be a link here.
Roy.