You're of course completely correct about getting the exact error message, and I'm an idiot for not having that handy. I've e-mailed one of the red hat users to ask him for the specific error message.

Your idea about $LANG is interesting. What I'm doing is this:

if (exists $ENV{LANG}) {
  $ENV{LANG} =~ m/^(..)/;
  $preferences{'language'} = lc($1);
}
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So if red hat sets it to "en_US.utf8", it seems that the language would still be correctly recognized as "en". However, I think it's very likely that something along the lines of what you're saying must be the problem. Just on general principles, I should probably also do more error checking and sanity checking on the language code I'm extracting from $LANG.