It's probably best if you start by just looking at the attached screenshot. See the cpu spikes in the usage history? I've been experiencing this type of thing a lot when browsing online. I have watched the list of processes, and I see that these cpu usage spikes all happen in firefox. I can't quite figure out why it keeps doing that, although I have some theories. It can get really annoying, though. For example, as I'm typing this post, sometimes the letters stop showing up for a second as I'm typing... and then it "unfreezes" and everything I typed in the meantime comes out all at once. (Meanwhile I see the cpu spike in my performance tracking software) I am pretty sure that the websites I have open affect this. For example, I think if I have gmail open, or the igoogle page, it seems to do this a lot more. I have tested having just a blank page of firefox open, nothing else, and the described phenomenon went away entirely. But still, I want to know what more knowledgeable people think: is this a reasonable explanation? That some certain websites cause it but not others? Or am I missing some piece(s) of the puzzle?