SSH channel forwarding fails on ieof

[Pugnator <ookami@xxxxxxx>]

I use libssh 0.5.2 binding for C under Linux. In my program I create SSH 
tunnel to XenServer. It worked perfectly until I updated to the most 
recent XenServer 6.2. After it ssh tunneling started failing with

[1] Analyzing banner: SSH-2.0-OpenSSH_4.3
[1] We are talking to an OpenSSH client version: 4.3 (40300)
[1] placing 18 bytes into channel buffer (stderr=0)
[1] Error : Channel opening failure: channel 44 error (2) Connection refused

On server side there is records in /var/log/secure:

Sep 24 20:12:10 proxima sshd[20782]: pam_unix(sshd:session): session 
opened for user root by (uid=0)
Sep 24 20:12:10 proxima sshd[20792]: Accepted password for root from 
10.250.144.221 port 55673 ssh2
Sep 24 20:12:10 proxima sshd[20792]: pam_unix(sshd:session): session 
opened for user root by (uid=0)
Sep 24 20:12:11 proxima sshd[16132]: channel_by_id: 0: bad id: channel free
Sep 24 20:12:11 proxima sshd[16132]: Disconnecting: Received ieof for 
nonexistent channel 0.
Sep 24 20:12:11 proxima sshd[16132]: pam_unix(sshd:session): session 
closed for user root


The most strange is the ssh server version is the same on old and new 
servers:
OpenSSH_4.3p2, OpenSSL 0.9.8e-fips-rhel5 01 Jul 2008

I'm not sure how to debug such an issue. Sometimes tunnel establishes 
and works but it is 1 out of 100 tries.