This just happened maybe 30, 45 minutes ago. I hadn't used my iMac in a few hours so I went to go on it and turned on the bluetooth keyboard and mouse, and it hadn't woken the computer up. I tried again to disconnect it, and reconnect my bluetooth mouse and keyboard. Nothing. I then tried to hold down the power button on the back of the iMac to see if it would turn on. Nothing. I had no choice but to unplug the power supply and replug it in. After that I held down the power button and it turned on just fine. Has anyone experienced that before yet on the new iMac 24 inch? Ive had this for 20 days and I love it so far, but that was the only thing that just happened today that was very odd. I do keep open a lot of tabs on safari so maybe that was why? Has anyone had this issue yet?