I started going through some seeds using random words I see on my desktop. It just so happens that I played Technic/Tekkit, so I figured I'd give them a try. I tried Tekkit first (single player, creative, map name of Tekkit, seed of Tekkit). It got to 'Building terrain' and then goes back to the main menu. Looking at the task manager I see java is taking up 3 of my 4 cores. Attempting to open the world again causes a full freeze of Minecraft. The same happens with Technic.