No, please be a pest. I'd prefer pest-like responses over none at all

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Hmmm.... so you click the open league button... navigate to the league folder "league.lg", and click okay... and it still gives you that error?
The only thing I could think of is to be absolutely sure you're selecting the correct league folder.
If you are, gimme a few minutes, and I'll do what I can to duplicate your problem.