asterisk users - May 2006 - Problem on Zap Channel with IVR

Hi to all.

My asterisk pbx has a tdm400p card with 2 FXO cards on it.
I configured the extensions.conf to send all the call incoming from that 
zap channels to an IVR system.
I see in the asterisk CLI the call incoming and the playback of the 
message custom/myfile but no sound is played on the channel, i cannot 
hear nothing.
If I change the configuration and i send the call to an internal sip 
extensions alla works great. Also works well when i configure a sip 
trunks to answer and playback the ivr message, i can hear it very well.

If I use the zap channel to do an outside call, all works well also.

Asterisk varsion is 1.2.7.1

This is my zapata.conf :

*Code:*

channels]

language=en
context=from-pstn
signalling=fxs_ks
rxwink=300              ; Atlas seems to use long (250ms) winks
;
; Whether or not to do distinctive ring detection on FXO lines
;
;usedistinctiveringdetection=yes
busydetect=yes
busycount=4
usecallerid=yes
hidecallerid=no
callwaiting=yes
usecallingpres=yes
callwaitingcallerid=yes
threewaycalling=yes
transfer=yes
cancallforward=yes
callreturn=yes
echocancel=yes
echocancelwhenbridged=no
echotraining=800
rxgain=0.0
txgain=0.0
group=0
callgroup=1
pickupgroup=1
immediate=no

;faxdetect=both
faxdetect=incoming
;faxdetect=outgoing
;faxdetect=no



and this is what I see in the asterisk cli during the call :

*Code:*

 -- Starting simple switch on 'Zap/1-1'
    -- Executing Set("Zap/1-1", "LOOPCOUNT=0") in new stack
    -- Executing Answer("Zap/1-1", "") in new stack
    -- Executing Wait("Zap/1-1", "1") in new stack
    -- Executing Set("Zap/1-1", "TIMEOUT(digit)=10") in new
stack
    -- Digit timeout set to 10
    -- Executing Set("Zap/1-1", "TIMEOUT(response)=10") in
new stack
    -- Response timeout set to 10
    -- Executing BackGround("Zap/1-1", "custom/benvenut0")
in new stack
    -- Playing 'custom/benvenut0' (language 'en')
  == Spawn extension (from-pstn, s, 6) exited non-zero on 'Zap/1-1'
    -- Executing Hangup("Zap/1-1", "") in new stack
  == Spawn extension (from-pstn, h, 1) exited non-zero on 'Zap/1-1'
    -- Hungup 'Zap/1-1'



I'm going crazy, please send me some suggestions.
Thanks in advance.
Bye