In the translation file "Luxembourgish.locale" file located in the directory "PortableApps.com\App\Locale" the file states that the language ID for Luxembourgish is 1033, but that is for English, the proper ID for Luxembourgish is 1134, according to the list of locale ID's provided by Microsoft here.
This will be fixed in the next release. I've made the change in the local set.
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I knew that it was probably being handled, but I couldn't see any documentation on it in the forums, so I thought it wouldn't hurt any to report it.
I had reported this for Beta 4 and reported it again for Beta 5 along with a number of other issues with languages. (But since then Microsoft has assigned it a locale ID.)
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