When I see consistent hard failure, I tend to assume an unrecoverable electronic failure (e.g. mobo and coffee don't mix). When I see intermittent failures - particularly when it seems to occur during boot (which kinda describes Shep's symptoms), my experience is typically a hard-drive starting to go south. I work in a company of about 50 people, and we've seen this happen to many of our laptops. So much so that we warn our users to let us know asap when they see similar symptoms. Catch it early enough and you can backup and restore to a new drive.