Strategy-Evolver-throws-InvalidOperationException

CODE:
System.InvalidOperationException: Collection was modified; enumeration operation may not execute.
   at WealthLab8.cwStrategyEvolver.EnableMethod(Object spec, ProgressChangedEventArgs cont)
   at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
   at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)