Sometimes my Mac Snow Leopard (version 10.6.1) randomly freezes up, and I can move my mouse, but I have the spinning beach ball of death. I can also move windows, but nothing is responding. This happens for several seconds, and then everything returns to normal. I use Firefox, which I know is a memory hog, so is that causing it? How can I fix this?
Just a note, this was happening before I upgraded to Snow Leopard. I got my computer in late June 2009, Unibody Macbook Pro 13".