asterisk users - Jan 2011 - Sangoma A104d / overlapdial=yes / dial with audio one-way issue

Hi,

I am facing an audio-problem with the dial application and I (!) think, 
that it is connected to the dahdi parameter "overlapdial=yes". Sangoma
support does not see any connection between this. But when enabling this 
option I face with some(!) dial-partners a audio one-way issue (the 
called party can not be heard). Only using PSTNS (germany e1 trunk) - no 
voip.

Is there any other setup out there with this issue?

Kernel: Linux 2.6.26-2-amd64 #1 SMP Sun Jun 20 20:16:30 UTC 2010 x86_64 
GNU/Linux
Asterisk: Asterisk 1.6.1.20 built by root @ xxx on a x86_64 running 
Linux on 2010-09-03 07:47:24 UTC
LibPRI: 1.4.11.4
DAHDI: 2.3.0.1 Echo Canceller: MG2
Wanpipe-Driver: 3.5.15
Sangoma-Firmware: 43 (Board A104d with echo hardware chanceller)

Typically this problem can occur with echo cancellaltion. But I do not 
think, that this is my problem.

Best regards,
-Thorsten G?llner-