This error is occurring because constituent records have duplicate primary addressee records.  Constituents can only ever have one primary record of any type, and in this case, many constituents in the database had two primary addressee records.  You can view this on the constituent records, but can also see it by running the following script.  The script will not change any records, but will provide a list of constituents with more than one primary addressee in your database.

select CONSTITUENTID, count(1)

from dbo.NAMEFORMAT NF

where NF.PRIMARYADDRESSEE = 1

group by CONSTITUENTID

having count (1) > 1