I'm running into the same issue (Windows 7, 64 bit).
No luck attempting to install repeatedly, tried switching the card back to 1.0, I can't really change the slot since I don't have a spare x4 pcie slot and I do not have an extra computer to do the upgrade on.
It seems like this is a common problem on Mac. Avid actually proposes to simply bring out an extra MacBook Pro to do the upgrade.
I'm confused both because Avid seems to think that that's an acceptable solution and also because last time I looked, a macbook doesn't have a pcie slot. I guess we should also have an external pcie box lying around?
Anyway, if anyone has a solution that would be very much appreciated.