Hi,
Just spent hours fiddling with the widcomm drivers on my laptop trying to get it to dial up Vodafone GPRS.
On a random thought, I removed the widcomm drivers and reinstalled my USB dongle with the XP SP2 ones.
I set the GPRS connection to use "standard modem over Bluetooth link" and it connected.
This is using a Nokia 6600, please report if it works with any other phones and I will add a note on my blog.

Cheers,

Rene / mobileKirjava
http://blog.kirjava.net.nz/?postid=36