Okay, so I got win64 the other day and then plugged my capture card in, I downloaded the latest drivers from the site (at the moment, it's version 3.9.1) installed them, rebooted the PC, a firmware update popped up, let it update, came up with an error. So I uninstalled 3.9.1, took out the disc that came with the card (the drivers on the disc are 3.4) installed the drives, rebooted the PC and windows kept freezing, I then took the card out and the freezing stopped.
That's the basic story. If anyone can help fix this, that would be highly appreciated.
Did you uninstall the 3.9.1 drivers first? I would do that with the card not in, delete the Blackmagic folder in your program files directory, Then start over with the drivers that you had it working with. Hope this helps, Danny Hays