The problem is that CF11 uses a version of hibernate in which boolean fields that contain NULL values are bugged in MS SQL. It is in the release notes and Adobe has shown no indication that they intend to update Hibernate in CF11 to fix it. I added a vote to the bug:
Bug#3518916 - Trying to inserting Null in primitive boolean type throws error for SQLServer
The workaround is to replace ormtype="boolean" with ormtype="numeric_boolean". I haven't tried this as we'd been holding off in the hopes that they would patch to a later release of Hibernate but no luck so far.
