Same for me. Someone posted that the game seems to clear the graphic card´s RAM (maybe some kind of garbage collection?), even on cards with more than 1GB. Maybe there is an easy way to fix the problem for cards with more than 1GB (like mine) in another patch.
This could also mean that running the game on the HD4000 on an i7 CPU might not encounter the “hanging” problem, though the game is slower from the start. Can anybody prove that? (I
ve got an AMD cpu and cannot test it, unfortunaltely)