Object reference not set to an instance of an object.

 I was wondering if anyone could help me with this error?
Error: Object reference not set to an instance of an object.
Source: App_Web_file_manager.aspx.e021b801.agdqgvav
User Name: admin
Producer Code: 00010b
Name: A&M A&M
__________
Page: /private_admin/file_manager.aspx
Query String:
Browser: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.0.11) Gecko/2009060215 Firefox/3.0.11 (.NET CLR 3.5.30729)
 Stack Trace:
    at _Default.GridView1_RowDataBound(Object sender, GridViewRowEventArgs e)
   at System.Web.UI.WebControls.GridViewRowEventHandler.Invoke(Object sender, GridViewRowEventArgs e)
   at System.Web.UI.WebControls.GridView.OnRowDataBound(GridViewRowEventArgs e)
   at System.Web.UI.WebControls.GridView.CreateRow(Int32 rowIndex, Int32 dataSourceIndex, DataControlRowType rowType, DataControlRowSt ...