I'm pretty new to Apple, Oct 2011, and must admit I'm an Appleholic now. Anyway, have any of you guys experienced issues with iMac when the computer sleeps and hard drives go off that when you return it from sleep (mouse click) a grey screen appears. When I move the mouse about the grey screen it shows the background where it then allows me to enter my password. When moving the mouse about the screen it's like 0.5cm size pixels slowly revealing the background through the grey. I've got 27", i7, 3.4Ghz with 8Gb RAM and AMD Radeon HD 6970M 2048 MB. Thanks in advance.