Can't edit datagrid with form variable

I am unable to edit a datagrid that is based on a dataset with a form variable. The datagrid is initially fine, with all the columns I specified and the edit button. When I click the edit button the datagrid clears and I am left only with the column labels. The datagrid is set to be invisible until the user selects a name from a list box, and when a name is selected the datagrid shows records for that name. I want the user to be able to edit those records without having to have all the other records displayed. What am I doing wrong? Is there another way I can display specific records for editing other than in a datagrid or is this the way to go?
Thanks