sme123joshyg

All it says when I try and load it up is, 'shutting down internal server' and then doesn't respond

I believe it's some sort of world corruption as I can load up new worlds fine, any ideas on how I can fix ?

Today, I tried logging onto my single player as normal. I loaded it and it got stuck on building terrain, I clicked the screen and the spinning windows loading symbol appeared and the minecraft tab went white. I've done some troubleshooting of my own and I believe the problem is to do with windows 8 java, I've tried giving it more memory, reinstalling java several times but nothing works. I'm open to any suggestions as to how I could fix this. -Josh