Yep, you made the fatal error of installing SP2, which (in my experience) completely hoses anything that deals with bluetooth.
Microsoft (in their wisdom) have decided to completely take over all BT workings, and not give 3rd party (aka better) BT drivers/software a chance of talking to the hardware.
I've experienced this on 2 computers with SP2.
TBH, I can't see ANY advantages of SP2 on an in-car computer...hell, i can't see any advantages on a home computer, as I have another system sitting next to me that takes 10 mins (or more) to log on/off. It's a P4 2.4 with 512mb ram, and I swear it's slower than when I installed XP on a P133 with 64mb RAM!