This has happened to my 2009 MacBook Pro, my mother's 2010 MacBook Pro, and just now to my brother's 2008 MacBook Pro. The solution in both mine and my mom's case was replacing the hard drive. Luckily my Mac was under warranty but my mom's was not and this ISN'T cheap when you have to foot the cost.
Solution: If your Mac is still under warranty call and arrange to have it repaired (usually at little/no cost). If not, just use it as a $2000 paper weight or bookend. In few words: nothing on the Apple support website or anything the Apple tech people on the phone told me to do worked to fix my problem.