>>>I have successfully added a combox to a DataGridView:
>>>
>>>

>>>DataGridViewComboBoxColumn colType = new DataGridViewComboBoxColumn();
>>>colType.HeaderText = "Total";
>>>colType.DropDownWidth = 90;
>>>colType.Width = 90;
>>>colType.MaxDropDownItems = 15;
>>>grdColumnInfo.Columns.Insert(0, colType);
>>>colType.Items.AddRange("", "Calc", "No Calc", "Pending");
>>>grdColumnInfo.Columns[7].DataPropertyName = "Total";
>>>

>>>
>>>In my SQL table is a column called Total. How do I set this combo to show the value from SQL?
>>
>>Try setting the DataPropertyName directly on colType:

colType.DataPropertyName="Total"

>>Check this:http://msdn.microsoft.com/en-us/library/system.windows.forms.datagridviewcolumn.datapropertyname.aspx
>
>This throws
>

>---------------------------
>DataGridView Default Error Dialog
>---------------------------
>The following exception occurred in the DataGridView:
>System.ArgumentException: DataGridViewComboBoxCell value is not valid.
>To replace this default dialog please handle the DataError event.
>

Sounds like a bit of debugging is called for.
One reason might be that the value for 'Total' in the table is not one of the items available to the ComboBox ("Calc", "NoCalc") etc.