Resolving Error Running Database Update: "Create Failed for Index..."?

Error running database update: Create failed for Index…

The following exception may occur during an Acctivate database upgrade if records exist with duplicate “key values”.  This problem is not very common, but it can potentially block a database upgrade until the duplicate key values are resolved.

Error running database update: Create failed for Index 'INVRegister_RegNumber'. --> An exception occurred while executing a Transact_SQL statement or batch. --> The CREATE UNIQUE INDEX statement terminated because a duplicate key was found for the object name 'dbo.tbINVRegister' and the index name 'INVRegister_RegNumber'.  The duplicate key value is (2631). The statement has been terminated.

For example, older versions of Acctivate potentially allowed multiple inventory transactions to be posted with the same session number (i.e., duplicates). However, the database cannot resolve the duplicate problems automatically during the upgrade.  The above message may appear and our support team may be required to re-assign the duplicate key values.