According to the so called "geniuses" at the Apple store, my main board needs to be replaced,. Approx $800 and no garuntees how long it will holdup. My machine was the top of the line iMac when I bought it in 2008. It's only 3 years old and now this? I'm running OS 10.5. I called Apple support and they said I did everything they could have told me to try... but still no response. So hense the appointment at the Apple store. I'm in a big bind here. This machine has all my work and over 10 years of material. I'm completely broke and cant afford a new box and need to get my machine back on line. I'm open to all suggestions. You're help is desperately needed. Thanks.