It would be helpful if you could list the brand and model of the computer.
Also, possibly helpful would be the outputs of:
Particularly to know if you have a 32 or 64 bit processor. When you say video player, I assume you mean flash? do you have a lot of ram, and are you trying to do a lot at once?
Alternately, if flash keeps giving you troubles, you could try switching to swfdec
[sudo apt-get install swfdec]