Hi guys:
I had exactly the same problem. Brought my Mac Pro in for other service and mentioned the bluetooth (wireless mouse) issue. They replaced the bluetooth card/antenna under warranty, but when they returned the machine to me, they’d also removed the Decklink card, saying it interferred with the bluetooth. Bluetooth mouse then worked fine. However, I need the decklink card to digitize beta tapes, and have just put it back in the machine. Once again, the Mighty Mouse is a bit slow at times, but much better than before. Apparently the bluetooth replacement helped.