I'd say that an actual disk drive failure is a serious possibility

If the drive is making nasty clicking noises and it wasn't doing it before, I would highly suspect the drive itself. Although, most drives that make the "click of death" don't work intermittently. They usually don't work at all.

*EDIT* just reread your post and realized the drive isn't working intermittently. You can probably get an RMA for the drive at the manufacturer website if it is less than 3 years old. Be aware that they may not do that with OEM drives though.