When I import Contacts from Excel (actually .csv format), everything seems to
work fine.  But when I open a New Message window and select "To..." and then
select the contact, the email address appears as a single dot (.).  

I have found that if I go into the Contact's property sheet and clear the
"Display As"  box, and then click in the box, it will re-create the display
name.  This seems to fix the problem (for that one contact), even though the
"new" display name looks exactly like the one I deleted.