could you remove the forums, drop any table pertaining to the forum and redeploy the forum ear ?
I downloaded the source.
Removed the portal and forums ear's
Deployed the ear's from the source.
Dropped "jbossportal" db (MySQL 4.1.11)
Recreated "jbossportal" db
I experience the same error....I was however able to take the same sql statement, at the point of failure, and run it sucessfully against db in MySQLBrowser.