I received same error message, and program crash, going back to try out 1.3.3. Great software.

After upgrade to DX10, or whatever the version MS currently have on their website, 1.3.4 and 1.3.4 work great

However, I'm still using 1.3.3 because there is a function that was missing in 1.3.4 and 1.3.4b, in 1.3.3 every windows of wow acted like they are on top, I can just do 1 click to skin/pick up item or target mobs, as for 1.3.2 and older + 1.3.4, this function seem missing, I have to go back the old way, click an instance to bring it on top, than do rest of the clicking in it.