[HELP] unexpected hangup

I need some help:

I’ve 2 asterisk servers: 1 of them on centos 4.5 with asterisk-1.2.24, asterisk-addons-1.2.7,asterisk-sounds-1.2.1 , libpri-1.2.5 & zaptel-
connected to and e1 via te120 and when teh zap call is bridged there is an unexpected hangup , i saw the logs and can see this:

Called g0/0059372588885
– Zap/3-1 is proceeding passing it to SIP/101-0a185480
– Zap/3-1 is making progress passing it to SIP/101-0a185480
– Channel 0/3, span 1 got hangup request, cause 1
– Hungup 'Zap/3-1’LI>
== Everyone is busy/congested at this time (1:0/0/1)
– Executing [s@macro-dialout-trunk:26] Goto(“SIP/101-0a185480”, “s-CHANUNAVAIL|1”) in new stack
– Goto (macro-dialout-trunk,s-CHANUNAVAIL,1)
– Executing [s-CHANUNAVAIL@macro-dialout-trunk:1] GotoIf(“SIP/101-0a185480”, “1?noreport”) in new stack
– Goto (macro-dialout-trunk,s-CHANUNAVAIL,3)
– Executing [s-CHANUNAVAIL@macro-dialout-trunk:3] NoOp(“SIP/101-0a185480”, “TRUNK Dial failed due to CHANUNAVAIL - failing through to other trunks”) in new stack
– Executing [50059372588885@from-internal:2] Macro(“SIP/101-0a185480”, “outisbusy|”) in new stack
– Executing [s@macro-outisbusy:1] Playback(“SIP/101-0a185480”, “all-circuits-busy-now|noanswer”) in new stack
– <SIP/101-0a185480> Playing ‘all-circuits-busy-now’ (language ‘es’)

and in the other server i have exactly the same situation but with differents modules(asterisk-1.4.11 , asterisk-addons-1.4.2 , libpri-1.4.1 , zaptel-

I really will appreciated if someone can help me, and please sorry for my english , i know is not good enough.

It’s any one’s guess as to why. Do you run zttool ? Any alarms ?

Also why don’t you just use IAX for trunking ?

Yes i already run zttool and i don’t have any alarm.

I not sure if my problem is a bug because i look for" span 1 got hangup request, cause 1 " on chan_zap.c, and in the start of this part of code i 've this:

#error please update libpri

I am no expert in T1/E1 trunking between both box’s. I would look at the configuration in zapata.conf and zaptel.conf. Also why don’t you use IAX trunking ?