How to handle NULL fields-error with fill method

I have a data adapter that is using a stored procedure and when I get to the fill method to fill a dataset I get the following error
Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints.
The results of the procedure has 6 columns by 50 rows with some NULL field values throughout so think the NULLs are causing the problem. Just wondering how to handle this? Thanks Paul.Fixed this problem. Since a change was made to the procedure, reconfiguring the data adapter cleared the problem.