It's a wierd issue

, let me try to explain what happens.
I have distribution lists in Outlook 2007. It might contain some 15 names inside it. When I make an email and want to send it to this distribution list and hit the send button, the distrubution list dissapears and all left there are a bunch of semicolons (the normal separator between email addresses). The message of course doesn't go out since there's nobody in the email address, but doesn't give an error or anything.
Do anybody know what I can do?

Just to give a little more data, this will happen with any distribution list, even new ones that I create, and if I just put all the names in the distrubution list individually in the To:, it will work fine and send the message.