Datagrid Index Out of Bounds

Hi,
I have a form with a datagrid that loads a modal dialog
when the f3 button is clicked. A value from a read only
datagrid in the modal dialog is double clicked, the modal
dialog is closed and the value is returned to the main
form's datagrid cell. This works fine but when I attempt
to tab out of the cell, I get an index was outside the
bounds of the array error, which is coming from the modal
dialog. I have tried things such as setting
currentrowindex but no success. Any ideas? Thanks in
advance.