Two times now, over the last 3 weeks my Mac Pro is failing to boot. Once on, it stays on the blue screen with the spinning icon and never gets to the login screen. To remedy this I boot from install dvd, re-install Leopard and only then will it boot completely. COuld this be my HD is getting ready to fail?
It will be best for you to run a S.M.A.R.T scan on the drive to see if its failing. You can do this by downloading the free trial of Smart utility.
If the hard drive turns out fine or passes the S.M.A.R.T Scan then just re-install the operating system after you've backed up your data obviously.