I was getting this same thing, your hard drive may have developed errors. If you have an install disk try to get into the Command prompt, its buried deep in the advanced options, from there do a full CHKDSK. Before you do that even, you should use GWscan to check it for read element failure, which that program can fix as long as there are not too many bad areas. If you at any time cancelled an Automatic Repair, like maybe you stopped it the first time, and then tried to reboot? I guarantee you it messed up your hard drive. I always say run GWscan first, because Windows 8 Auto Repair cannot repair those kinds of errors. Once you check for read element failure, run CHKDSK from the Install disk command prompt. THEN you can try to boot normally, it should then run the Auto Repair full cycle.
There may be other issues preventing boot, but I always start from the assumption that Windows 8 had fouled up my drive, which is has several times in the past. 9 out of 10 boot problems I have had were all basically read element failure that after I repaired, the OS worked perfect.