I had this problem as well. I had deployed the DemoSite to Tomcat using MySql, then switched to HSQL, then back to MySql. After switching back to MySql, I got this error above.
did not help. All references to HSQL were correctly changed back as far as I saw it.
My solution was to create a mysql database under a new name, so instead of "broadleaf" I created a new one named "blf" and the error was gone.
I had tried to drop and re-create the database "broadleaf" under the same name before, but still got that error. So it seems that something was cached somewhere, but I still could not figure out, where.