You should go to safe mode, then to device manager and delete all the Yamahas in the list under sound devices category. This removes a lot of possibly confusing things and may enable operation again, but in worst case you're gonna have to do a reinstall.
Different PCI slots maybe be worth trying too, after the devices have been cleaned up from device manager.

I read somewhere on the Internet a similar problem with this card. There was only one solution, reinstalling the operating system with the card installed initially.