to provide a complete solution, we need to know the exact steps that led to the error. So far our best guess is: you converted a file infobase to a server one. File databases do not check their records for uniqueness and this is why duplicate keys were detected.
If this is your case and you get the error when you restore the infobase from a .dt file, try the following:
1. Open the file infobase and run verification and repair (in Designer, on the Administration menu, click Verify and repair).
2. Save your file infobase as a .dt file and then load it to your client/server infobase.
If this does not help, please describe the steps that led to the error and we'll find a proper solution.