My 2 week old iMac is really slow at times doing a variety of tasks. It's Finder, copy, paste, inserting rows in an Excel spreadsheet, all over the map. I get the happy spinning rainbow wheel, and wait upwards to 15 seconds for tasks that should be instantaneous. I've run disk utility, it says the hard drive is fine. I seemed to have a jillion disk permission issues, I asked it to repair those, it did (and when I reran they were all gone) but still, no joy. Ideas?