Using iMac early 2009, with OSX 10.9.4. Been working fine until now. Every few minutes, the curser changes to a spinning wheel, and the computer freezes up for 1-3 minutes. The curser (spinning wheel) will move with the mouse, but nothing works. If I try to force quit, even that won't happen until the curser changes back to normal. Thought it might be slow internet connection, but it happens even when not online. Often happens when scrolling...just freezes up for a few minutes. Any suggestions would be greatly appreciated.