#1 h.264 codec video transmission problem

[Anonymous]

The company that I work for is implementing the H.264
and H.263+ video codecs in its software. Recently there
has been a problem where the H.264 will work when
transmitting to most users but not between two users
that can transmit to the same other user. So Computer
A and B can transmit to Computer C but not to each
other. This problem does not exist with the H.263+
codec. Any suggestions on shat could be causing this
problem?