Indeed there was an incompatibility if a device running V12 firmware tried to register at a PBX with V11 if H.323/TCP or H.323/TLS was used. The fix is available in V11r2 build 113363 and later:

http://download.innovaphone.com/ice/download/p/published/Firmware%20Version%2011r2/113363/

Many thanks for the bug reports and informations regarding this issue !