Error: An error occurred in the Duplicate Search: Error 91: Object reference not set to an instance of an object.
Error occurs when importing constituent records with International Addresses via Import-O-Matic.
Check the duplicate criteria in The Raiser's Edge to remove the State and replace with Zip Code (first 3 digits).
The State is listed as one of the duplicate criteria. Because many international addresses do not include a state, this caused an error in Import-O-Matic.