Hi there.
I have had the same problem as you for some time now. But i have now found a solution to it!:
1.open the game normally...
2.kill just the game in task manger(not RunDll32)
3.leave rundll32 running and re-open the game but this time open the game as administrator....
4.the game  will open but rundll32 will still take up heaps of CPU. so once in the game Alt-Tab it out, and kill rundll32,there for leaving your computer with normal CPU  and the game to run normal again.
hope this helps. with regards.....