editable gridview cell events

[Robert Smith]

Hi,
I'm using a gridview control in my asp.net page, however I'm getting an
unhandled exception when I click on one of the editable textbox cells after
first clicking the edit command button and then clicking the textbox field
that I wish to edit. Please tell me what event gets triggered when you click
on an editable cell in a gridview.

Thanks in advance
Robert
My gridview is as follows:

<eo:CallbackPanel ID="cbpTargetGroup" runat="server" Width="100%"
GroupName="SysTargetGroup"
Triggers="{ControlID:gvwTargetGroup;Parameter:gvwTargetGroup}" >

<strong>Target Groups</strong>
<div class="container" style="overflow: auto; width: 300px;
height: 350px";>
<asp:GridView ID="gvwTargetGroup" runat="server"
AllowSorting="True" AutoGenerateColumns="False"
OnRowCommand="gvwTargetGroup_RowCommand"
OnRowEditing="gvwTargetGroup_RowEditing"
OnRowCancelingEdit="gvwTargetGroup_RowCancelingEdit"
OnRowUpdating="gvwTargetGroup_RowUpdating"

OnSelectedIndexChanged="gvwTargetGroup_SelectedIndexChanged"
OnRowCreated="gvwTargetGroup_RowCreated"
OnRowDataBound = "gvwTargetGroup_RowDataBound">
<RowStyle CssClass="row" />
<AlternatingRowStyle CssClass="alt_row" />

<Columns>
<asp:TemplateField HeaderText="Edit">
<EditItemTemplate>
<asp:ImageButton
ID="imgCmdUpdate" runat="server" CommandArgument="UpdateItem"
CommandName="Select"


ImageUrl="~/Images/Informs/add.GIF" ToolTip="Update Target Group" />
<asp:ImageButton
ID="imgCmdCancel" runat="server" CommandArgument="CancelItem"
CommandName="Select"


ImageUrl="~/Images/Informs/goback.GIF" ToolTip="Cancel Edit Target Group" />

</EditItemTemplate>
<ItemTemplate>
<asp:ImageButton ID="imgCmdEdit"
runat="server" CommandArgument="EditItem" CommandName="Select"


ImageUrl="~/Images/Informs/edit.gif" ToolTip="Edit Target Group" />
</ItemTemplate>
</asp:TemplateField>

<asp:BoundField DataField="TargetId" ReadOnly
="True" />
<asp:BoundField DataField="TargetName"
HeaderText="Target Name" SortExpression="TargetGroup" ReadOnly="True" />



<asp:TemplateField HeaderText="Is Active"
SortExpression= "Is Active" >
<ItemTemplate>
<asp:Checkbox id="chkIsActive"
Runat="server" Enabled = "false" />
</ItemTemplate>
<EditItemTemplate>
<asp:Checkbox id="chkIsActive"
Runat="server" Enabled = "true" />
</EditItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText ="From Insight"
SortExpression="From Insight" >
<ItemTemplate>

<asp:Checkbox id="chkFromInsight" Runat="server" Enabled = "false" />

</ItemTemplate>
</asp:TemplateField>
<asp:BoundField DataField="IsActive"
ReadOnly="True" />
<asp:BoundField DataField="SourceId"
ReadOnly="false" />

<asp:CommandField ShowSelectButton="True">
<HeaderStyle CssClass="HideButton" />
<ItemStyle CssClass="HideButton" />
</asp:CommandField>
</Columns>
<AlternatingRowStyle CssClass="alt_row" />

</asp:GridView>