Cause: Advanced Queuing requires that the agent's dblink name should be unique within the first 24 bytes (for 8.0 compatible queuetables) See the solution below.
Error solution: Specify a dblink name that is unique within the first 24 bytes or migrate to 8.1 compatible queuetables where this restriction is not there.
Database version: Oracle 11g Release 2 (11.2)