I have a series of maps of Eastern Europe, in which many place names use the Polish barred "L" (ł). The labels are in Centaur typeface, and they have always displayed fine, until now. Today, that letter display as a square box. If I copy-and-paste to another software (Word, or Notepad, say) again it displays fine, so I know that the character is correct and that both Windows and the typeface support the letter. But Xara suddenly does not.

What can I do to fix this?