I am getting what I consider an odd error when using a databound
combobox.  I use 1 dataset with 4 tables, each filled with a different
data adapter.  3 of them are lookup tables which are bound to 3
different combo boxes.  The 4th table is the main table (Equipment) of
data.  I then bind many different textboxs to the Equipment table, as
well as the 3 comboboxes, a bound checkbox, and a bound
DateTimePicker.   I can edit records and navigate the records with no
problem.  Here is the weird part, when I create a new record using
Me.BindingContext(dsData, "Equipment").AddNew(), it blans all of the
fields out just like I would expect, I then set the comboboxes value
to 0 to make the first record the selected record:
       Me.cboHost.SelectedValue = 0
       Me.cboDepartment.SelectedValue = 0
       Me.cboMount.SelectedValue = 0
When I attemp to save the record I call endcurrentedit:
Me.BindingContext(dsData, "Equipment").EndCurrentEdit() .  I then get
an error that the field cboHost does not allow null.  When I console
display the SelectedValue of the combobox, it says the value is 1.  To
get around this, I can click in the combobox and change the value to
something else, then change it back, and no problem.  What is the
reason why setting a SelectedValue at runtime in a combobox makes the
currencymanager think the value is null, and what can I do about it?

Here is the relevant parts of my code:

Private Sub BindFields()

       txtID.DataBindings.Add("Text", dsData, "Equipment.ID")
    cboHost.DataBindings.Add("SelectedValue", dsData,
"Equipment.HostID")
       txtBuilding.DataBindings.Add("Text", dsData,
"Equipment.Building")
cboDepartment.DataBindings.Add "SelectedValue",dsData,
"Equipment.DepartmentID")
       txtRoom.DataBindings.Add("Text", dsData, "Equipment.Room")
       txtJack.DataBindings.Add("Text", dsData, "Equipment.Jack")
       txtCable.DataBindings.Add("Text", dsData, "Equipment.Cable")
       txtPair.DataBindings.Add("Text", dsData, "Equipment.Pair")
       txtName.DataBindings.Add("Text", dsData, "Equipment.Name")
       txtTN.DataBindings.Add("Text", dsData, "Equipment.TN")
       txtNumber.DataBindings.Add("Text", dsData,
"Equipment.FullNumber")
       txtPrefix.DataBindings.Add("Text", dsData, "Equipment.Prefix")
       txtExt.DataBindings.Add("Text", dsData, "Equipment.Ext")
       txtACD.DataBindings.Add("Text", dsData, "Equipment.ACD")
       txtType.DataBindings.Add("Text", dsData, "Equipment.Type")
       txtModel.DataBindings.Add("Text", dsData, "Equipment.Model")
    cboMount.DataBindings.Add("SelectedValue", dsData,
"Equipment.MountID")
       txtDES.DataBindings.Add("Text", dsData, "Equipment.DES")
       txtRollup.DataBindings.Add("Text", dsData, "Equipment.RollUp")
       txtVM.DataBindings.Add("Text", dsData, "Equipment.VM")
       txtFDN.DataBindings.Add("Text", dsData, "Equipment.FDN")
       txtHunt.DataBindings.Add("Text", dsData, "Equipment.Hunt")
       txtVMRevert.DataBindings.Add("Text", dsData,
"Equipment.VMRevert")
       txtNCOS.DataBindings.Add("Text", dsData, "Equipment.NCOS")
       txtRNP.DataBindings.Add("Text", dsData, "Equipment.RNP")
       txtSCC.DataBindings.Add("Text", dsData, "Equipment.SCC")
       txtComments.DataBindings.Add("Text", dsData,
"Equipment.Comments")
       chkInactive.DataBindings.Add("Checked", dsData,
"Equipment.Inactive")
    dtpInactiveDate.DataBindings.Add("Text", dsData,
"Equipment.InactiveDate")

       AddHandler Me.BindingContext(dsData,
"Equipment").PositionChanged, _
               AddressOf UpdateStatusForPosition

   End Sub

If Not IsDirty(dsData.Tables("Equipment")) Then
  Exit Sub
End If

Private Function IsDirty(ByVal tbl As DataTable) As Boolean

       Console.WriteLine(Me.cboHost.SelectedValue)

       Me.BindingContext(dsData, "Equipment").EndCurrentEdit()

       Dim dr As DataRow
       For Each dr In tbl.Rows
           If dr.RowState <> DataRowState.Unchanged Then
               'it's dirty
               Return True
           End If
       Next

       'not dirty
       Return False

End Function

If you need more information, please let me know.  I am at witts end.

Thank you
Kalvin