Datagrid cell delete/esc combinations yield dll null reference exception

I am using the process of posting back to the datasource as a device to catch certain errors made to the data in a datagrid. (The datagrid is linked to the corresponding datatable via a dataview.) Doing so seems to work, as the datagrid then shows the row highlighted by the "error provider" icon (red circle with exclamation mark). When I then double click on the cell to select its contents, press delete, then press escape, I get a System.Forms.Form.dll "NullReferenceException." I cannot find where to put the handler to catch this event. Does anyone have any ideas on this

Incidentally, other combinations of keystrokes and datagrid editing seem to work fine

Thank
Jack Herr