At first, I thought the bug was probably Prat's fault, since Prat is the most chat-oriented mod I'm using. However, after taking a look at my Lua errors, I traced it down to CraftyGnome, which I have disabled for the time being. I've heard of this error being caused by a few mods, though, so if you're running any of:
- An old version of Deadly Boss Mods
Try turning them off (or updating, in the case of DBM) and see if that fixes the problem. And if you've found any other mods that you have verified as causing this issue, let me know and I'll add them to the list.