This is almost certainly MySQL corruption, which is not something that can easily be fixed.
Try running a mysqlcheck and see fi that fixes it. If not, it an OSRestore and restore the backup file you made before the upgrade.
Running MySQLCheck on Brightmail Gateway 7.7 or higher:
Log in as support user to the Command Line Interface (CLI) on the appliance with Control Center .
Run the following command:
/opt/Symantec/Brightmail/mysql/bin/mysqlcheck -h127.0.0.1 -ubrightmailuser -p`cat /data/etc/.brightmailuser` brightmail --auto-repair
During the run of the above command, take note of any table names that may fail the repair. (i.e. spam_message, spam_message_summary...) as these will need to be repaired manually.
Note: The acute symbol ( ` ) used in the -p switch is the one under the tilde ( ~ ) and not the one under the quotation marks ( " ).
After MySQLcheck has finished it is recommended that a restart of the Control Center service as well as the MySQL service be preformed:
To restart the services, log in to the CLI as admin.
enter the command:
service mysql restart.
After service restarts, enter the command service:
controlcenter restart.