asterisk users - Jul 2004 - Zaptel Hung Up on x101p and cisco analog line

I'm having many troubles with x101p (orginal from Digium, wcfxo kernel
module)
on analog line simulated by a Cisco Router
I'm experiency random hung up while zaptel doesn't recognize call
progress
(Italy signalling)
Signalling is simple ignored as if someone hangs up on the other end of the 
analog line, on the asterisk end is it possible to listen the busy tone as 
generated from cisco router without hang up Zap channel
On other calls a sort of hangup detect causes random hangup. (I've tryied
with
an analog phone and is not a cisco problem is related to asterisk)

my question is:
How is it possible to correctly detect call progress (callprogres=yes is for 
US signalling) or to ignore completely call progres to stop theese random 
hangup?

Help please...