Random Waterfox Lag

So for the past, probably, half hour, I've been streaming Pandora in Waterfox (a 64-bit variant of Firefox for those that don't know) and browsing around NBR and every once minute or two, Waterfox will kind of freeze up and stop responding for a second or two (music stops) and then it will start responding again and work fine. It doesn't normally do this and I can't figure out why it's doing it all of a sudden. According to Task Manager, my CPU usage is consistently around 10% (fluctuating about 5% both ways) and my physical memory (which I'm guessing is RAM) is at 65%. My internet connection is fine. I truly am stumped as to what the problem is. I deleted my paging file today, but I don't think that could be it since I don't seem to be getting even close to 8GB. Any ideas as to what the problem could be?

EDIT: it seems to occur when I click a link or change tabs. As I typed this, it stayed fine, but when I submitted it, it did it again.
It also did it as I tried to exit out of a tab.

 

Check your add-ons. Usually they are the source.