Description: Exception in server tick loop

java.lang.IllegalArgumentException: Don't know how to add class thaumcraft.common.entities.EntityAspectOrb! Report this error to mod author.
	at net.minecraft.entity.EntityTrackerEntry.func_151260_c(EntityTrackerEntry.java:717)
	at net.minecraft.entity.EntityTrackerEntry.func_73117_b(EntityTrackerEntry.java:434)
	at net.minecraft.entity.EntityTracker.func_72788_a(EntityTracker.java:334)
	at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:1010)
	at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:432)
	at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:841)
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:693)
	at java.lang.Thread.run(Unknown Source)