First of all, this is the message I get:
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Adventure Game Studio
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An error has occurred. Please contact the game author for support, as this is likely to be a scripting error and not a bug in AGS.
(ACI version 3.12.1074)
Error: Single word too wide for window
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OK
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This happens whenever a GUI containing a listbox becomes visible while OPT_RIGHTTOLEFT is set to 1. As a quick explanation, that option displays the game's text from right to left, in the style of Hebrew and some Arabic languages.
In addition, the text of buttons isn't influenced by this option at all. This exception can actually be put to good use in some situations, but it's still an unexpected behavior.
Workarounds for both issues are already in place in my case, so consider this just a bug-report, not a help-request.
I don't know if the issue has been addressed already in newer version of the engine, in which case I apologize for the waste of time. If you think I should add this report to the bug-tracker as well, please tell me and I'll do with pleasure. So much time passes between one visit to this boards and the next that I tend to forget AGS-etiquette and customs.
3.12 is rather old now, this should be tested with latest, or at least 3.2.1 (last version made by Chris Jones).