So this morning it failed to boot up on the internal drive. Boot started and it shuts down. Started with OPTION pressed and boot successfuly from external drive. This error message occured ..... So it appears to be a hard drive issue but wait ....... Ran " SMART Utility " to test the drive and it tests 100% clean. Still I do not trust the HDD .... so replacing it is on my agenda. But then tonight ...... While running off the external HDD I experienced a random shiutdown. Got a message saying " restarted due to a problem ....... send report to apple " Before sending a report I looked at and printed the details ...... but it's doesn't make sense to me. ALSO while running off external HDD (USB) I am getting a lot of the spinning beach ball thing at times. Trying to determine if I should go ahead with HDD replacement of is something more sinister lurks inside the iMac. I will post the fault report in the next post ----- maybe someone can see a problem and point it out.