I have a form that allows the users to enter quite a few variables for selection criteria. Those are passed to a method in the business object. I am getting an error "Object reference not set to an instance of an object" when I try to run the form. I have checked to make sure that the class name matches and that there are valid values in each of the parameters being passed. I set a breakpoint to verify that the values are correct. The error occurs immediately upon executing the call to the business object. I have also tested the business object code in the test bench and it works correctly there. This code worked before switching to MM .NET 2.4. I have run out of ideas for things to try next. Any help is greatly appreciated.

The code from the form and business object are listed below.

Form code

    public partial class MedicalReviewMaint : mmBusinessForm
    {
        private MedicalReview oMedicalReview;
        private Client oClient;
        private Patient oPatient;

        /// <summary>
        /// Constructor
        /// </summary>
        public MedicalReviewMaint()
        {
            oMedicalReview = (MedicalReview)this.RegisterPrimaryBizObj(new MedicalReview());
            oClient = (Client)this.RegisterBizObj(new Client());
            oPatient = (Patient)this.RegisterBizObj(new Patient());

            InitializeComponent();
. . .

        }

        private void btnLocateRecord_Click(object sender, EventArgs e)
        {
             //Get medical review records meeting selected criteria
            this.oMedicalReview.GetMedReviewsBySearchCriteria(this.cboLocClient.SelectedValue.ToString(),
                this.txtLocClientPatientId.Text,
                this.txtLocLastName.Text,
                this.txtLocFirstName.Text,
                this.txtBegDate.Text,
                this.txtEndDate.Text,
                this.cboLocReviewBy.SelectedValue.ToString());

business object

[Code to build command string and parameter array.  MRSqlCmd is a StringBuilder, ParamList is a parameter array]


            this.GetDataSet(MRSqlCmd.ToString(), CommandType.Text, ParamList);
            return this.Entity;