I've been having a problem since I bought my first iMac a few days ago with the screen going black a couple of seconds after turning it on, meaning I have to switch it off and back on again to get it to boot properly. I phoned apple and they went through telling me to unplug the power cable and hold the power button for ten seconds, and then starting it holding four of the keys down, but they also said that I shouldn't switch the power off at the wall every night as apparently this can cause problems. I was just wondering if anyone else has been given this advice and whether it's true or not. It seems a bit silly that I can't unplug my iMac without apparently causing problems.