I have no clue what this means, but it has been popping up when I run my walkthrough. It does not appear to disrupt my game however. Any clues?

System.InvalidOperationException: Collection was modified; enumeration operation may not execute.
at System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource)
at System.Collections.Generic.List`1.Enumerator.MoveNextRare()
at System.Collections.Generic.List`1.Enumerator.MoveNext()
at System.Linq.Enumerable.Any[TSource](IEnumerable`1 source)

You get that error if you try to change a list (or a dictionary I guess) in a foreach loop - in particular remove an item. For example this will:

l = Split("one;two;three", ";")
foreach (s, l) {
  if (s = "two") {
    list remove (l, s)
  }
}

Will it cause a problem for my game play?

Potentially, yes. Presumably you had a good reason for removing the thing from the list, and if that does not happen that would be a bad thing.

Can you work out where it is? What is happening in the game when it appears? Does that indicate a script or function to look at?

On go Tools - Code view, and [Ctrl]-F and just search for "foreach"; if you do not have many, that could be the quickest way.

I have zero "foreach" scripts (I did search in code view to confirm). I have never used them. Actually, I have no clue what they are or how they would work. I've never removed anything from a list or dictionary. It only appears when I play from my walkthrough. I click close and go about testing my game. I do not think it happens if I play the game from the beginning to the end, but then again, I am trying to avoid doing that for now because it takes such a long time to play to test without using the walkthrough.

EDIT: The last five or six times running the walk through I have not experienced an error message, so... I guess I just cross my fingers and hope for the best.

Thanks again, Pixie.

If it just happens on the walk through, but not when you do exactly the same things in the same order in play, then I would ignore it.

Do you use timers at all? Because walkthroughs happen so fast, they can behave differently when there are timers.

Nope. No timers. Enough people bitched about the one timer I used in X1, so I decided against it! lol