Minecraft crashed

Put the summary of the bug you're having here
Crashed upon opening server

What I expected to happen was...:
Describe what you thought should happen here
Enter server or tell me insufficient space

What actually happened was...:
Describe what happened here
Kicked off game, recieve 3 crash reports from one crash

Steps to Reproduce:
1. Open minecraft
2. ...play cubecraft with 64bit java
3. ...