Try to rename the file 'prefs.prop' stored under 'my documents/telltale games/<name of episode>' to something like 'prefs.old'.
As far as I know all the settings you make on the main menue (like graphic level, volume, hint level, screen resolution, etc.) are stored in this file. If the game cannot locate that file, I guess it
should start with some common defaults...
I have not tried this procedure myself, so
I cannot guarantee that it works, but if the game just does not start at all without that file or you get some other strange effects, you can still change back the file name. (That of course would not help you with your problem then, but what I am trying to say is that at least you do not risk anything by trying my suggestion as you can restore the current state any time if it does not work.)
Edit: You could also try to use a 'prefs.prop' file Telltale provided here:
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This was meant for "Fright of the Bumblebees", but perhaps it works for the other episodes, too!?
(Again, I have not tried this myself, so make sure to backup your original 'prefs.prop' file for that episode first before you replace it.)