That error is often thrown when you run an Excel solution on a computer that
has Windows regional settings other than English (United States). Have a
look at this article:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/odc_vsto2005_ta
/html/OfficeVSTOGlobalization.asp

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Harry Miller
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> I get this error on this line of my VSTO Excel code
> Exception from HResult: 0x800A03EC
> mainMenuBar = ThisApplication.MenuBars["Menu Bar"] as CommandBar;
>
> what could be wrong?