I am running 10.5.6 on 2008 Mac Pro with 8GB RAM and have been experiencing "extremely" slow, choppy response suddenly in the past day. When I drag a window around the screen, it's choppy and stuttered and when I press and hold a key like thisssssssssssss, the repeat rate is super slow and uneven, even though I have it at the fastest setting. Also, I'm a fairly fast typer and as I type, words come out in spurts, like there is a latency issue. Is it perhaps a memory or graphics issue? I'm wondering also if it could be related to an app called "Onyx" I recently installed, or some other application running in the background sapping resources. It's very disturbing and reminiscent of a new PC before you install the video drivers. Is there a way to check processes that may be running on startup, like AutoRuns for PCs?