I Am Running A BukkitForge Server With Crafting Dead: Cure From Tekkit! I See People Are Trying To Join My Server And They Get Protocol Error??? My Friend Was Playing With Me On The Server. BTW Crafting Dead Requires 1.5.2 If That Help. Please Help!!!!
I suspect those people don't have Tekkit installed, or at least the Crafting Dead mod-thing. You can safely ignore those messages.