Engineering WorkBench (V6.1) Error

I have a production person that is modifying a BOM and when she tries to make changes

to the Bill after being checked out, she gets an error "More than one ECORev records found

by a unique find. (3166). I checked every component in the Bill and cannot find any problems.

There are two revisions to this assembly, but none are approved.

Does anyone have any words of advice?

V6.1 was before my time, but, I see this in one of our V6.1 KBs (excerpt):

First, assume that the indexes have been corrupted. Run an index rebuild. It is possible that the indexes were corrupt and did allow duplicate records to be created. However, the first step is rebuild indexes.

If this does not fix the problem, contact Vantage Technical Support for further assistance.