What are the details of this system? How much RAM, for example.
How many videos are you running at once? Which web browsers?
Have you tried cleaning out the temporary internet file caches?
After streaming a few videos all my web browsers turn up a plain white screen. Sometimes its after 30 minutes sometimes after an hour. My IM programs still work fine.
I'm running Windows 7 and have Bit Defender as my anti-virus. I have Time Warner Cable and it never did this when I had DSL. Any.suggestions will be much appreciated.