I have a late 2008 iMac which will slow, show colorful confetti (I call it) and then crash. Although there is an occasional gasp of processing, it will require a cold boot to recover. This happens only when on multi media pages, but not all of them. I am up to date with Symantec, have all the latest upgrades, have tried in safe mode, etc., and even reformatted the drive. Still the problems persists. I realize the iMac is old and an upgrade might be in order, but I have no idea when the next iMac refresh will be, and otherwise the iMac works fine. Can anyone offer any ideas???