I have the same problem with Ubuntu 13.10. The whole system freezes for anything from about 15 - 60 seconds after loading a large image in Firefox or using Google maps in satellite view. While it is frozen you cannot move the mouse or do anything. When it comes out of the freeze everything then works as normal... until the next freeze up! Very annoying. This problem started after upgrading to Ubuntu 13.10.
I found that if, when you boot up the computer, you select in GRUB the linux kernel which was used in ubuntu 13.04 ( 3.8.0-34-generic ) this problem does not occur.