A couple of times in the past month or two I have needed to restart my iMac in safe mode after force quit due to frozen screens. When I reach the log in screen and enter my password the desktop comes up but there are white bars scrolling vertically until the iMac loads the desktop completely. I am wondering what these white, scrolling bars might portend. I was with Apple Care on one of these occasions and he stated it might be a hardware issue but left it at that and said not to worry. The iMac is now two years old and works like a charm but I am wondering what I might be in for; if anything. Thanks.