Today, I've received the following error a few times while out questing:
Carbonite.Quests\NxQuest.lua:10086: bad argument #1 to 'band' (number expected, got nil)
[C]: in function `band'
Carbonite.Quests\NxQuest.lua:10086: in function `CalcDistances'
Carbonite.Quests\NxQuest.lua:8549: in function `func'
Carbonite\Libs\AceTimer-3.0\AceTimer-3.0-17.lua:55: in function <Carbonite\Libs\AceTimer-3.0\AceTimer-3.0.lua:48>
The error occurred occasionally while I was in combat, but a quest was attempting to updating its status. Once combat ended, the error stopped occurring. It also panics Blizzard's LUA scripting system because it will also spit back a system message in the chat pane about an addon generating lots of errors during the event.