Whenever I play YouTube videos in Firefox, it snags. Sometimes it's every 10 seconds, sometimes it's every 20, sometimes it's every 5. This effect fluctuates during playback, but for the most part it behaves like a pulsar.
I monitored Firefox using Process Explorer set to take snapshots 2 times per second, and as you can see by the enclosed pic, each time there's a snag, firefox spikes in CPU usage, and a little bit in RAM usage ("private bytes"). It's the only process or app doing this, the others don't reflect any change relative to those spikes.
When I visit the same page using IE or Chrome, the video plays fine and there are no spikes. I've tried disabling all add-ons in Firefox and it still happens.
Any idea what might cause this? or where I should proceed from here?