I have the Iogear GBU301 bluetooth wireless USB adapter, and it worked perfectly before I did the SP2 install. I've now uninstalled and reinstalled it 3 times (with the Widcomm 1.4.2 driver), with the same result. Windows says it's found my new hardware and installs all kinds of drivers and software and then says it's working, but when I right-click on the blue/red bluetooth icon in the system tray, it says "bluetooth device not found". Rebooting makes no difference.
I only use bluetooth to sync my iPaq 2215 once in a while, but this is an annoying glitch, and - touch wood - the only problem with the SP2 install I've encountered.