addItem to table with hbnContainer (org.hibernate.exception.ConstraintViol)

Hi, I’am rather new to Vaadin, and I’m starting a project using it it combination with Hibernate and SQL Server as database. I have a simple table containing an generated integer id and a description field. The database does not allow this description to be null.
I have a class to extend table for this. This uses an HbcContainer as data source.
Following the example on the Vaadin wiki I perform an addItem on the table to create a new record.

System.out.println("*** before add ***");
Object newLanguage = languages.addItem();
System.out.println("*** after add ****");

Looking at my console I see that hibernate fires off some queries to determine the generated id for the record. (At this moment with description null allowed )

*** before add ***
Hibernate: insert into meta.language (language) values (?)
Hibernate: select count(*) as y0_ from meta.language this_
Hibernate: select top 100 this_.languagecode as language1_1_0_, this_.language as language1_0_ from meta.language this_ order by this_.languagecode asc
*** after add ****

However, when this record is inserted when the description is not allowed to be null, then the following error occurs:

Caused by: org.hibernate.exception.ConstraintViolationException: Cannot insert the value NULL into column ‘language’, table ‘newSizingAssistant.meta.language’; column does not allow nulls. INSERT fails.
at org.hibernate.exception.internal.SQLStateConversionDelegate.convert(
at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(
at org.hibernate.engine.jdbc.internal.proxy.AbstractStatementProxyHandler.continueInvocation(
at org.hibernate.engine.jdbc.internal.proxy.AbstractProxyHandler.invoke(
at $Proxy6.executeUpdate(Unknown Source)
at org.hibernate.persister.entity.AbstractEntityPersister.insert(
at org.hibernate.persister.entity.AbstractEntityPersister.insert(
at org.hibernate.action.internal.EntityIdentityInsertAction.execute(
at org.hibernate.engine.spi.ActionQueue.execute(
at org.hibernate.engine.spi.ActionQueue.addResolvedEntityInsertAction(

Do you have a good hint how a get around this problem without having to change the restrictions of the database?