It seems to be gone now, but did anyone else catch the the link to sign up for an account at the bottom of the main google search page today? Either they're just about ready to finally launch for real or, since it's gone now, they were just trying to get more testers since they've probably exhausted invites as a way of doing this.
It may not be the usual click, but it still sounds like a dying drive. Maybe it's just one bad sector, but this is a point to take no chances. I wouldn't turn it back on until you have your backup/rescue option in hand.