Two BT-PhoneModems at one Netebook

The Situation:

One Notebook with an AcerBT500 BT-Dongle and latest WidcommDrivers
One Nokia6310 with provider "A"
One SonyEricssonT610 with provider "B"

I'v set up
-two BT-Modems, one at COM9 and the second at COM11,
with the initstrings for the different phones
-two DialInNetworkConnections for both Providers,
linked the right modem th them
-linked the DialUpNetworks from both phones to MyDevices
connected to the DialInNetworkConnections

It works perfect for both phones IF you turn of both phones and
turn on the one you want to use as modem.
If both phones are turned on it depends on which one was turned
on second - this is the one that is exclusivly used as modem,
ignoring all other settings. If I turn off this one the connection goes
to nirvana - you have to turn off and on the other phone to use it
as modem.

I'v spend _hours_ on this, any Idea how to handle this problem?

regards
Christian