Crash Report: https://gist.github.com/ace5852/687fcb2ab34019c5591f
Someone on my server crashed the server which left the above crash-report. There is a no such method error relating to a spell. I'm thinking something to do with lightning bolts (SpellLightningBolt.onOffensiveMeleeRightClick)

Minecraft 1.7.10
Java 7 Update 65 OpenJDK
See crash report for more details.

Try this with one of the Beta builds and come back if it occurs again. :3