Slow iMac 24
My iMac has recently started hanging up with the spinning beacball, sometimes as long as 20 seconds, in all apps, but specifically INDD CS5
iMac (24-inch Early 2009), Mac OS X (10.6.8)
In Disk Utility run a Disk Repair and check your S.M.A.R.T. status of the drive. If you aren't using a backup plan now would be a good time to start. Your drive may be giving up the ghost.