SQL Error

05/26/2014 23:18 Little Messi#1
when i try to set identity for refobjcommon and refobjchar i get this error


'_RefObjChar' table
- Unable to create index 'PK__RefObjChar'.
The CREATE UNIQUE INDEX statement terminated because a duplicate key was found for the object name 'dbo._RefObjChar' and the index name 'PK__RefObjChar'. The duplicate key value is (18004).
Could not create constraint. See previous errors.
The statement has been terminated.

any one know how to fix it ?