[Freeswitch-users] ZRTP - SAS-strings not the same

Hi, I got freeswitch working perfectly on CentOS 6.3 by following the guide on http://wiki.freeswitch.org/wiki/Installation_Guide. Then I followed the steps listet at http://wiki.freeswitch.org/wiki/ZRTP to get ZRTP working. Now, when I do calls from a zrtp-enabled client to another, communication still works BUT the sas-strings showing up on the clients aren't the same. Now my question is: why? Does anyone have some troubleshooting-tips for me? What possible reasons are there? Thanks in advance for any help. Greetings, Finn