Phantom duplicate value error

[joldavidson]

I am trying to establish a relationship between tables in PowerPivot and keep receiving the same error about there being duplicate values in both columns, in spit of the fact that one of the columns does not have any duplicate values. The error message is as follows:

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Error Message:
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The relationship cannot be created because each column contains duplicate values. Select at least one column that contains only unique values.

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Call Stack:
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at Microsoft.AnalysisServices.Common.RelationshipController.CreateRelationship(DataModelingColumn sourceColumn, DataModelingColumn relatedColumn)
at Microsoft.AnalysisServices.Common.RelationshipController.CreateRelationship(String fkTableName, String fkColumnName, String pkTableName, String pkColumnName)
at Microsoft.AnalysisServices.Common.SandboxEditor.erDiagram_CreateRelationshipCallBack(Object sender, ERDiagramCreateRelationshipEventArgs e)
at Microsoft.AnalysisServices.Common.ERDiagram.ERDiagramActionCreateRelationship.Do(IDiagramActionInstance actionInstance)

Any help would be greatly appreciated.

[MattAllington]

Are there any blanks? Blanks can cause this error too