I'll try that and see what happens. I keep getting the same error that I need to download the new flashplayer, which I already have done.
Tried reloading firefox and no dice. It still doesn't work.
Try loading any video on youtube.com , if it loads correctly then flash plugin doesn't have any problem.
Also try downlaoding newer version of flash player plugin to your firefox browser from site http://get.adobe.com/flashplayer/.
Try installing the flash player on the firefox.It is because of the either flash player not present / lower version of flash player on the firefox browser.
Installing should solve your problem.