Most likely you would have to hack a class in the org.hibernate.dialect package. I filed a Hibnernate JIRA a while ago with a patch, but till now such kind of problem is not get fixed. Okay, first know which dialect you are using. Most likely MySQL5Dialect. That class extends the MySQLDialect. You can open the source code of org.hibernate.dialect.MySQLDialect.java and add the column type you want (make sure your mysql jdbc driver support this type), or write a java class called org.hibernate.dialect.MySQLPatchedDialect.java, and rebuild the hibernate.
I am stuck with the same problem. I am using MySQLInnoDBDialect. Any solution would be appreciated.
Just a note. Using MySQL5Dialect, I get this error for TEXT datatype also.