NDT 1.04 Error when merge...

Hi guys! Maybe someone could help me with this. I have imported 3 version in NDT and should do a merge but got follow error: -“Duplicate index value. Operation aborted”. This will occure both when i select Merge Wizard and Merge Setup. The import of the diffren version are made tru “Import from Navision Klient”. Someone seen this problem, and have a solution? Best Regards Per Bay