Hi, I noticed this problem a few time since I bought my iMac 21,5" 3.06ghz 4gb ram (late 2009) on october 2009 Sometimes it happens that iMac freeze also for very simple task (ie selecting some files inside finder), I see the small wheel multicolor and it stalls so until I move the mouse (wheel multicolor) on the dock of the app at the bottom of the screen, when I do that the iMac come back normally. I don't use heavy application of editing video/audio, I configured my iMac for 2 account (me and my girlfriend), she use only browser with a dozen of open tab (tab, not windows) sometimes 1 word doc (office for mac), that's all for her. I use some server app for iphone (airvideo, wine server,xmarks) or backgrounding app (little snitch, eyetv) and I use moreover browser, itunes + tune up, iphoto, imovie, transmission, quicktime. I noticed that very often my problem occurs when I select files in a finder window or itunes window open eyetv screen window open video in quicktime there is not a rule, but it seems to be related to video activity Because of I was thinking that the reason was the ram, I bought 2x4gb of new ram, so now I have 2x2gb of ram installed by the manufacturer plus 2x4gb of new ram, for a total amount of 12gb, but the problem is still here I tried to reinitialize macosx, to repair permission, to verify hard disk, to perform apple hardware test, to perform memtest/rember, all test were passed with OK I tried also to reset PRAM/VRAM and to reset SMC.... I dont'k know whatelse try... all seems to be ok, but I experience the problem yet. Someone could please help me and suggest something???