DTMF problem

Hi,
Im having some problem with my DTMF on my IAX line : When I make a call from my SIP softphone (Idefix now Zoiper) If i send DTMF the calle never receive them.
What i see in the console with debug and dtmf set to on :

 -- Executing [15143102355@diamondcardterm:1] Dial("SIP/test-081ed8c0", "IAX2/diamondcard/15143102355") in new stack
    -- Called diamondcard/15143102355
    -- Call accepted by 64.124.128.5 (format gsm)
    -- Format for call is gsm
    -- IAX2/diamondcard-1 is making progress passing it to SIP/test-081ed8c0
[Sep 19 11:29:10] DEBUG[13963]: chan_iax2.c:7017 socket_process: Ooh, voice format changed to 2
    -- IAX2/diamondcard-1 answered SIP/test-081ed8c0
[Sep 19 11:29:26] DTMF[16849]: channel.c:2408 __ast_read: DTMF begin '0' received on SIP/test-081ed8c0
[Sep 19 11:29:26] DTMF[16849]: channel.c:2418 __ast_read: DTMF begin passthrough '0' on SIP/test-081ed8c0
[Sep 19 11:29:29] DTMF[16849]: channel.c:2408 __ast_read: DTMF begin '0' received on SIP/test-081ed8c0
[Sep 19 11:29:29] DTMF[16849]: channel.c:2418 __ast_read: DTMF begin passthrough '0' on SIP/test-081ed8c0
[Sep 19 11:29:34] DEBUG[16849]: chan_iax2.c:3099 iax2_hangup: We're hanging up IAX2/diamondcard-1 now...
    -- Hungup 'IAX2/diamondcard-1'
  == Spawn extension (diamondcardterm, 15143102355, 1) exited non-zero on 'SIP/test-081ed8c0'

My iax.conf :

[diamondcard]
type=peer
username=XXXXXX
secret=XXXXXXXXXX
disallow=all
allow=gsm
host=usgw.ast.diamondcard.us

And my sip.conf :

[test]
type=friend
secret=XXXX
username=test
callerid="test" <5142222222>
host=dynamic
nat=no                      
canreinvite=yes              
disallow=all
allow=gsm                    
context=diamondcardterm

Ok I tried both rfc2833 and info setting in sip.conf , if I use the first one asterisk seems to receive de DTMF twice ! But the problem is not there …
Is there something I can do to make the DTMF pass throught or is it my IAX provider fault …
Thanks

I have never had this issue so I can not really comment but as a guess try setting your codec to Ulaw. Also try a different provider and see what happens.