Thanks for reading my post...I know the title is supposed to be descriptive, but my situation is so weird, I don't even know where to begin. I've brought my 20" 2008 iMac into the Apple Store twice (maybe three times?), but each time I bring it in the computer is on its best behavior, doesn't really slow down, etc.. The first time the geniuses suggested I clear my caches...which I did. Second time, they suggested we bump up the RAM. We bumped the RAM (4GB now), but the computer still spends over half of its life spinning the beach ball. There are moments (30% of the time, perhaps?), when the computer works properly and zips along. The hard drive is mostly empty, and we generally use nothing more than a browser. The Apple folk have run their diagnostic tests each time we've brought the computer in, but haven't found anything. I'm pretty much convinced that it's a hardware issue...but how to figure that out if Apple can't figure it out? At one point it was giving me just a grey screen when I booted up (sometimes with the prohibitory sign in place of the Apple logo one expects at start-up). I ended up reinstalling OSX (using the archiving option), but it didn't have any effect (it fixed the grey screen issue, but the computer still barely moves). The issue might have something to do with the browsers (in particular Firefox and Chrome). The computer is often fine as long as the browsers aren't running. Most recently, when I run Safari it doesn't show up as running (it's running, but when I do Command+Tab, it doesn't appear as one of the applications that are running). Often, when the computer is not working properly, I've noticed that in Activity Monitor there's the message, in red, "Finder not responding." In addition to OSX, I've also reinstalled Firefox and Chrome. Even after reinstalling Firefox, it continues to crash (usually before it even loads). Safari more or less works...but Gmail doesn't work properly, it begins to load, but never ends up showing the inbox (I'm able to access other sites, though). My gut feeling is that it's either the hard drive or the motherboard, but wouldn't that type of issue have shown up when they ran the diagnostic? *Any* thoughts would be much appreciated!