When I upgraded from Mac OS X 10.6.0 to 10.6.1, suddenly my 2006 iMac became a sluggish beast, trashing the disk for every little thing that it needed to do. Changing to another virtual desktop became 10 seconds of pure torture instead of a slick swish… At first I thought this had nothing to do with the upgrade, and thought my disk might be going bad.
Onyx, the all-in-one swiss knife of maintenance tools that I ran found out that I had a disk error. I fixed this by rebooting with the Leopard install disk and using disk utility there to correct the error. But my iMac kept being sluggish. Launching programs became an interminable wait (ok, ok, 10 seconds are not interminable, but they do add up in the long run when you want to get things done !)
Now that I upgraded to Mac Os X 10.6.2 things are suddenly running smoothly once again. I don’t know what happened, but they did something !