Adding organization; "This field is required"

Hi, I have a weird problem, I think. I'm trying to add a new organization, but it keeps telling me that "this field is required" beneath the "Parent" dropdown-list. However, the only choice in that list, is "--------". This might be a really stupid question, but I can't seem to get it to work... I'm running NAV 3.8.2 on Debian Squeeze. -- Joachim