Yes, I have these gaps every 5 seconds where the system is unresponsive. They get longer and longer. Really annoying when typing a post.
I think it's a firefox issue. Many have had the same problem although not recently. Perhaps I was using a shortcut to the 32-bit version and should be using the 64-bit version. But that doesn't solve the problem for me, I think. Still testing.
If I can't fix this soon I will try another browser.