Hello, We have had a first gen iMac since Feb of this year. It was flawless until August. Since then the Logic board was replaced because the fans wouldn't spool up enough to keep it cool. When we received it back the wireless reception sucked until a undate now it sucks again. The unit has never went to sleep on it's own since the LB replacement. A week and a half ago it started a random shutdown, Apple replaced the power supply last week and tonight it shut down twice again. Is this thing a lemon? We have converted the whole household over to Mac. This iMac, my Macbook, the kids 12" iBook, with two iPods. To date my MB has seen service for heatsink sensor and the above frustration with the iMac. Are we asking to much to has something we paid that much for just work. Do you think Apple will exchange this unit or allow us to pay the difference to go up to a 24"? Any and all help is greatly appreciated.