Word 2007 / Outlook 2007 integration problem

I have a problem with Word 2007 dying every time I try to use Mailings > Envelopes. I click on the Address book to open the Outlook 2007 Contacts list to select a mailing address to use as either a return address or mailing address and as soon as I select the contact's address, Word bombs out with an error. I have run the Diagnostics and it can't find anything wrong with either Word or Outlook. Any ideas?