asterisk users - Nov 2005 - bysy tone when dialing out via SPA-3000 in the netherlands????

Hi,

I want to use an SPA-3000 connect my dutch kpn PSTN line to and from the 
Asterisk VOIP network.
Dialing in (via my kpn pstn line) is functioning oke, with a great sound 
quality.
Dialing out to the pstn line produces after a verry short ring a busy signal.

If I connect the pstn to my Internal phonecentrale (kpn homevox) I will get a 
distorted dial signal (bothe when dialing directly (8) out or via a complete 
number).  With that signal I can dial my homevox extensions.

Doe anyone know how to solve this problem??? I guess the SPA-3000 is not 
interpreting the phone signals correctly or there is some timing problem?????

Any help greatly appreciated.

extensions.conf
[pstn]
ignorepat => 8
exten => _8.,1,Dial(SIP/${EXTEN:1}@pstn-spa3k,60,)

sip.conf
[pstn-spa3k]
type=peer
auth=md5
host=10.1.1.41
port=5061
secret=geheim
username=asterisk
fromuser=asterisk
dtmfmode=rfc2833
context=from-sip
insecure=very
;reinvite=no
;canreinvite=no


Output from the Asterisk console.
-- Executing Dial("SIP/1001-5748", "SIP/8@pstn-spa3k|60|")
in new stack
    -- Called 5219342@pstn-spa3k
    -- SIP/pstn-spa3k-c2e5 is ringing
    -- SIP/pstn-spa3k-c2e5 answered SIP/1001-5748
    -- Attempting native bridge of SIP/1001-5748 and SIP/pstn-spa3k-c2e5
  == Spawn extension (from-sip, 8, 1) exited non-zero on 'SIP/1001-5748'