So this morning had a spinning wheel and couldn't do anything except a force shutdown. On restart I get 5 green lines down the screen Which then goes to the white screen where it stays. I can use cmd R but doesn't seem to be a problem with the SSD, but haven't been able to get into safe mode. So a trip to apple store tomorrow, not confident that a reinstall of lion will fix the problem. Is a mid 2011 top spec imac that have had for 17 months, so glad I took out apple care.