asterisk users - Sep 2010 - Successive Dial apps give hang up within 30s!!

Hi All,
I am using an Asterisk 1.6.2.6, and when I use this part of the dialplan:
exten  => 8355,1,Dial(SIP/${EXTEN}&IAX2/${EXTEN},18,tTWwr)
exten => 8355,n,Dial(IAX2/8366,48,tTWwr)
(i made that simple to exhibit issue)

I got just 1 ring in 8366 extension before it hangup, what i noticed is the
total time spent on ringing is 30s that means if i use 12s in the first dial
i get 18s left in the second dial used (and so on)
i looked to the debug and cut the spot where it weirdly hang up:

localhost*CLI>
[Sep 29 20:02:32] DEBUG[21183]: chan_iax2.c:9726 socket_process: Packet
arrived out of order (expecting 3, got 2) (frametype = 6, subclass = 12)
localhost*CLI>
[Sep 29 20:02:32] DEBUG[21183]: chan_iax2.c:9733 socket_process: Acking
anyway
localhost*CLI>
[Sep 29 20:02:34] DEBUG[21184]: chan_iax2.c:10261 socket_process:
Immediately destroying 3477, having received hangup
localhost*CLI>
[Sep 29 20:02:34] DEBUG[5752]: channel.c:1760 ast_hangup: Hanging up channel
'IAX2/8366-8884'
[Sep 29 20:02:34] DEBUG[5752]: chan_iax2.c:4978 iax2_hangup: We're hanging
up IAX2/8366-8884 now...
    -- Hungup 'IAX2/8366-8884'
[Sep 29 20:02:34] DEBUG[5752]: app_dial.c:2315 dial_exec_full: Exiting with
DIALSTATUS=CANCEL.
[Sep 29 20:02:34] DEBUG[5752]: pbx.c:4306 __ast_pbx_run: Spawn extension
(OFFICE_EXTEN,8355,2) exited non-zero on 'IAX2/USPBX2-3477'
  == Spawn extension (OFFICE_EXTEN, 8355, 2) exited non-zero on
'IAX2/USPBX2-3477'
[Sep 29 20:02:34] DEBUG[5752]: channel.c:1655 ast_softhangup_nolock:
Soft-Hanging up channel 'IAX2/USPBX2-3477'
[Sep 29 20:02:34] DEBUG[5752]: channel.c:1760 ast_hangup: Hanging up channel
'IAX2/USPBX2-3477'
[Sep 29 20:02:34] DEBUG[5752]: chan_iax2.c:4978 iax2_hangup: We're hanging
up IAX2/USPBX2-3477 now...
[Sep 29 20:02:34] DEBUG[5752]: chan_iax2.c:4995 iax2_hangup: Really
destroying IAX2/USPBX2-3477 now...
[Sep 29 20:02:34] DEBUG[5752]: chan_iax2.c:2540 sched_delay_remove: schedule
decrement of callno used for 208.79.76.130 in 60 seconds
    -- Hungup 'IAX2/USPBX2-3477'

does anyone can guess what is hepening?
Thanks you!

-- 
Abdullah
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