bluetooth pairing problem

I have a Dell Inspiron 1720 laptop which has Bluetooth enabled. My Nokia 2760 phone also has Bluetooth enabled. I've paired them before and the phone is listed in the Dial up box but shown as disconnected. When I try to connect I get Modem Error 777. My phone can find my pc but not the other way round. I thought I'd try to Add a device but in the box that comes up there's no option to do that neither is my phone listed there.

I've used Bluetooth with my phone in the past so can anyone tell me what's gone wrong?
Let me remind you that there's no option to Add a Device in the Add Bluetooth Device box.

I'd appreciate some advice please. Many thanks.