Nokia 6630 problem with Windows Vista

I'm facing a peculiar problem with Internet connections...

I have a Nokia 6630 (v6.03.08) and a GPRS Connection to internet. I earlier had a Windows XP SP1 notebook and used a DKU-2 cable to connect to the internet, which worked pretty well.

However, I've recently upgraded to a Windows Vista Home Premium machine, and am trying to connect using the internal Bluetooth module. (it's using Microsoft Stack, v6.0.60). Over bluetooth, it gets connected with the network icon in the taskbar showing "Local and Internet". However, after a random time (5 minutes to 2 hours), the connection changes to "Local Only". At this stage, the phone is still connected to the internet (phone's Connection Manager), however, I cannot access any websites from the PC.

I have to disconnect and re-connect for the system to work again, but even that's temporary.

Also, in Vista, my phone does not get recognized with the DKU-2 cable (I've tried with seperate working ones). It does connect using the CA-53 cable tho (which seems strange, since they're supposed to be electrically similar).

Now, with the data cable connection, I'm getting pretty stable internet, it's gone "Local Only" just once, and I had the Bluetooth active with the PC at that point also...

... Any suggestions you may have at this stage will be most helpful!!