FATAL: terminating connection due to administrator command

Good morning,

      Through web application, once in a while(totally twice), we got
      the following fatal error message. May I know what may cause the
      error message please?

           org.postgresql.util.PSQLException:
        FATAL: terminating connection due to administrator command

           PostgreSQL 8.3.18 on x86_64-unknown-linux-gnu, compiled by
      GCC gcc (GCC) 4.1.2

      Without any coding changes, just re-run it, everything went well.
      So, I'd like to get comments what may cause "FATAL: terminating
      connection due to administrator command"?

      Thanks a lot!
      Emi