Duplicate user in pg_shadow

Hi

 When I do a SELECT * FROM pg_shadow, I can have more than one user with the same id. This caused the pg_dump to
 fail.

 I read that it happened in v7.1.2 and I am currently using v7.3.2 on Redhat v9.0

 What can be the causes and how do we rectify it?




Thank you,
REgards.