See: http://dev.mysql.com/doc/refman/5.1/en/connector-j-reference-configuration-properties.html "...The use of this feature is not recommended, because it has side effects related to session state and data consistency when applications do not handle SQLExceptions properly, and is only designed to be used when you are unable to configure your application to handle SQLExceptions resulting from dead and stale connections properly..."
Thanks for the report. This has been fixed in trunk, 6.0.x, 5.5.x and 4.1.x and will be included in 6.0.21, 5.5.28 and 4.1.40 respectively.
*** Bug 48080 has been marked as a duplicate of this bug. ***