Error message when importing .po file where the last string is untranslated

I'm importing translations to localize.drupal.org, and some of the imports end with error messages like:

The translation file modules-fieldgroup-panels-content_types.po ended unexpectedly at line 24.

The line number is one greater than the number of lines in the .po file (so in this example, the file had 23 lines).

I found that when the last string in the file is untranslated, I get this error message. When it's translated, everything's OK.

Weirdly enough, the import appears to succeed also when I get the error message. I tested this by importing a file which gave an error message, then translating the last string and importing it again. The second time, I got

The translation was successfully imported.
(number of strings) translations unchanged.

I got the files by extracting them from our old translation server (potx 5.x-1,3, l10n 5.x-1.0-alpha-3). But I did try to import one of the failing files to a Drupal site, and that went fine, so I assume the problem is with the import at the l10n server.

I've attached a few example files, so others can try to recreate the problem. The big file is all of CCK, the small file is modules-fieldgroup-panels-content_types.po (from CCK), both for 6.x. The language is nb (Norwegian bokmål).