Video streaming lag on all websites?

[john]

My computer isn't slow the videos load all the way through before I try to play them but anytime I watch a video on youtube or any other video streaming website the video stops but the audio keeps going for a short time then it eventually stops too. Moving the mouse over the screen when the video plays keeps it going for a short amount of time. It doesn't lag like this when watching a dvd or even netflix but anything else is impossible to watch. I've tried clearing my cache and everything but nothing has worked. I use firefox if that helps anything and also my computer hasn't always done this it just started a few months ago. What could be the problem and how can I fix it asap?

[Boss]

Maybe you will need more bandwidth from your ISP.