Interesting. What happens when it stops working? Does it just not buffer?
If so try refreshing. I'm just curious cause I've had no problems with it.
Which Mime type are you using (check the plugin options) I am using the
quicktime one over the windows media player. Also you have to have Gnash
installed for the plugin to work because flash (don't install flash) is a
requirement for the plugin
The HTML5 and webM thing
(http://www.fsf.org/news/free-software-foundation-statement-on-webm-and-vp8).
webM is free software but pretty much the only free browser that supports it
is firefox 4. However firefox 4 is still in beta stages and is not scheduled
to be released until early 2011 (https://wiki.mozilla.org/Firefox/4/Beta).
Firefox however is blacklisted from Trisquel
(http://libreplanet.org/wiki/List_of_software_that_does_not_respect_the_Free_System_Distribution_Guidelines#firefox)
because it recommends non-free software. Since only version 4 supports webM
you can DL and install the beta. Just be careful not to install any
proprietary add-ons or extensions. Or you can just wait until firefox 4 is
released and icecat follows.
Let me know cause I want to help you get this working. If you can maybe post
a screenshot for me to see.