1.       Sort the Query by name
2.       Run the Export
3.       If you are able to run a partial Export before this error occurs, open the Export and see what record it ran up to
4.       Open the Query and open the next record that should have exported
5.       Open the Constituent record, address records, relationship records to see what is causing the error
6.       Delete and recreate the record causing the error

If the above steps do not resolve this error, please follow the steps below until the issue is resolved:

1.  Create a new constituent query with the same criteria as the original.  Select this new query on the General tab of the export.
2.  Create a new constituent export with the same output fields as the original.  Select the new query created in Step 1 above to use with this new export.