music videos not loading in firefox

i am running XP- Pro, using all the latest flashes, etc. i am unable to get music videos to load from websites, even from myspace.com users profiles ...... was having a sound issue, but that is now solved....got rockin audio, but no video..... all i get when i try to view a music video is a completely black box where the video should be seen..... whats up ? same thing happens with IE..... needs ur help! thanks, deb