Set the buffer
and internet connection for your streaming app (player) a to little larger cache and a little slower speed.
Depending upon the app (DIVIX, Flash, QuickTime, other) there are different places to do all this but generally looking at Preferences (or control clicking the video window will open a preference pane) where you can set your network speed (wireless is always slower than a LAN cable) and your buffer AKA cache.
If there is a lot of traffic on the internet, that server, or your ISP (a very common occurrence - ISPs even limit the number of bits you can down/up load in a given time) streaming will slow. If it slows too much you run out (use up) your buffer or cache of video. The app will pause until the stream returns or the buffer is full enough to support play.
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