error in Lab 6-1 from MCAD training kit 70-306/316

I was trying to make the labs in this book but for some reason it doesn't
work. In this lab you first create a typed dataset using the xml designer
and then you use the data form wizard to create a master-detail form to view
and update data. I can load the data from the database but i can't update the
data in the database. I looked at the solution on the cd but here also the
update function doesn't work.
anyone got a solution for me?

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