Zoiper phone with SIP trunks.

I was trying to switch to Zoiper soft phones from eyebeam. I get the voiper phone to register to the asterisk server and I can place calls directly through the Zoiper soft phone. But I can't get vicidial/asterisk to place the inbound call to the Zoiper phone to start a session. Can anyone tell me what additional things I may have to do for Zoiper that I didn't have to do for Eyebeam? I am also looking for a script to work with Fire Fox for one click calling. I have a script for Eyebeam that works with Grease Monkey and Fire Fox.