I have a 20" 2.16 ghz C2D iMac with 2 GB of RAM. I've always been able to run multiple applications and still get great performance out of Photoshop (and the others as well), but for the last few days, it has been extremely sluggish, to the point that when I move a layer, it is jumpy and sometimes moves only parts of it at a time. I have not added anything new that I can think of so I just can't figure out what is going on. Right now, I have two browsers, adium, Linotype Font Explorer, Mail and Photoshop open and it is really sluggish. It reminds me of (gasp!) how my PC would act before I'd take it in and have the OS reinstalled. Any ideas what is going on?