asterisk users - Aug 2004 - extensions => s,1,Dial(Zap/2/number) noise

Hi,
       I'm trying to answer a call on one line and dial out a number on 
a zaptel x100p fxo, but all I get from the phone I'm dialing is silence 
after it is picked up, and on the line that's supposed to be dialed out 
itself, noise.

Thanks,
Imran