I get this error on my screen whenever I run my home-made waypoint. My waypoints end right under wherever I have found an herb, and I am in range of said herb when I add the waypoint.
Now I just got this one on my Western Plaguelands route:
[DEBUG] FiniteStateMachine Exception :
System.InvalidOperationException: Collection was modified; enumeration operation may not execute.
at System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource)
at MyWoW.FiniteStateMachine.Engine.Pulse()
at MyWoW.FiniteStateMachine.Engine.Run(Object sleepTime)