Server 1.8 crash when misplacing a block

[PappaJHR]

I have a little 1.8 server that I run for my children, a few friends, and myself. Our Minecraft client will crash whenever anyone accidentally tries to misplace a block. For example in the crash report below, I tried to place a mine cart onto the top of a sand block. I don't know what is causing this crash, whether it is Forge or one of the mods I am running. I am hoping that someone here can help me identify what is causing this crash. I posted both the crash report from the client machine and from the server (the server never actually crashes).

 

 

http://pastebin.com/sA6m16Pt

[LexManos]

 

        at noppes.npcs.ServerEventsHandler.invoke(ServerEventsHandler.java:160)

Seems like a issue stemming from the NPCs mod.

[PappaJHR]

Thank you very much for taking a look and replying to this...