I never had this issue in Vista x86, but with my new "supercomputer" I see this in the Device Manager.

It's the Bluetooth dongle for my Microsoft Wireless Entertainment 8000 Keyboard/Mouse Combo.

The 1st one showing there is a Bluetooth-enabled 28-in-1 media card reader that's installed in optical drive bay #3.

Apart from some issues where I have to reinstall the mouse and keyboard occasionally when booting between Vista and Windows 7 (shows the same there too), they work.

Well I think I answered my own question by disabling the Dell device. It seems that Bluetooth stacks can only accomodate 1 adapter at once, although I could swear I had 2 going in XP a while back.