It is bizarre. SP2 introduces native Bluetooth support to XP. Sounds really good until you discover that it really only allows you swap files with another device. So, you can swap photos with your phone, but not sync outlook/phone numbers/etc
Unfortunately, the 3rd party drivers that you had to use (when XP didn't have Bluetooth support) must have made use of some software shortcut that you aren't supposed to use, as the secure XP now stops the software from using it, thus breaking it.
Took me 3 hours to get XP to talk to the 3rd party drivers again. Grrrr. Still can't use the software that I used to use.
Not totally MS' fault as they did say that if you use software shortcuts, they are likely to be broken by SP2. Shame that WIDCOMM didn't release SP2-compatible Bluetooth drivers.
Further details here