windows media services problem

[edus]

I configurated an streaming server with windows media services in
windows server 2003 standard edition and I did a simple test
I opened the streaming with internet explorer 8 and also with firefox
3 (both with the latest updates) trought a client PC. The server and
client are over the corporate lan.

Using firefox the streaming never stops or do a disruption but using
internet explorer the streaming stops each randoms times and
rebroadcast again, sometimes the streaming stops directly and doesn't
auto begin.

I don't idea what may be hapenned, I tested with different clients pc
with different version of internet explorer (from xp, and windows 7)
and I obtain the same result.

What can I do?