cross platform video card upgrades seem to bring out all sorts of issues. that being said, i've experienced your error 43 issue transitioning from ati driver to ati driver so the issue is not exclusive to nvidia-ati driver swaps or vice versa. the ticket i submitted to amd suggested uninstalling the microsoft visual c++ stuff. it didn't work for me but maybe it might work for you. if all else fails, it may be time for a complete os overhaul. i think this will be my solution as well to finally get my x38 crossfire machine up and running again. good luck.