NAT Continually Redailing

I have set up NAT on a W2K server OK. Clients can connect OK and initiate the demand dial connection (when the problem BELOW hasnt already connected).

The problem is that although I have set it to only demand dial, it (on the majority of occasions) dials my ISP as soon as I plug the modem into the phone line!
If I disconnect it using the routing & remote access mmc /routing interfaces/modem, it immediatly dials out
again.
It disconnects after periods of inactivity
set in mmc/routing interfaces/modem-properties/options
(set to Demand Dial-Idle Time 1 Min &Redial attempts1-
Average Redial interval 1 Min). But then immediately dials out again!
Any Ideas?

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