Launching Minecraft

I was trying to launch Minecraft through the new launcher but it has only worked once, and that was on before I had wiped and reset my system's hardrive. Now it still has the same problem and has yet to launch, and I can't quite understand what is going on in the code. Since I first launched it will never completely download the files for some reason, then stop launching and say a crash has occurred (as shown in the crash report).

Steps to Reproduce:
1. Launch the Minecraft Launcher
2. Login with Minecraft account (I've tried both my old account and one of the new Mojang accounts that use email in place for a username but neither work)
3. Press play, then the loading bar stops 3/4 of the way to completing