USB bluetooth adapter not working

Hello! I have been using a Belkin USB Bluetooth Adapter to connect a magic trackpad to my early 2009 Mac Pro (since the built-in bluetooth is sketchy at best). This setup has worked seamlessly for a long time, but recently my computer stopped recognizing the adapter. What's curious is that my trackpad will still connect to the built-in bluetooth with minimal functionality, but the system shows that there are no bluetooth devices available (the icon on my menubar is crossed out and the bluetooth system preference is unavailable).

I installed the Mountain Lion supplemental update that was released on October 3, since its description says that it fixes issues with some USB bluetooth adapters, but my problem persists. I have also tried resetting my SMC. I want to exaust all software-related possibilities before I conclude that the adapter is broken and spend money on a new one. What else can I try? Thanks!