AJAX :: Update Panel In Gridview Footer

On my aspx page, I'm having troubles when I have an update panel within the footer template of a gridview. It appears to be an intermitent problem that occurs on subsequent postback when you do a delete command in the gridview. The first delete command always goes through fine (first postback). Clicking on another row to delete on the gridview (or any other button on the form) triggers this error: An error has occurred because a control with id 'ctl00$SupremeContent$grdLineNumbers$ctl09$ctl00' could not be located or a different control is assigned to the same ID after postback. If the ID is not assigned, explicitly set the ID property of controls that raise postback events to avoid this error.

If you click the back button in the browser, then click on another page, then come back to this page, you can delete another record. Another attempt to delete another record brings you back to the above problem. Thectl00$SupremeContent$grdLineNumbers$ctl09$ctl00 changes each time you delete, come back to the page and delete. If I disable the udpate panel, there's no errors. The reason I have the update panel is so that the user can select the relevant pipe specification (they see multiple columns using a textbox, drop down extender, panel and gridview) without the form's data being reset by the embedded gridview's selected index changed event. I've been trying to figure this out for a month now. Oh ya, this form is within a master page.

Here's the gridview code:

[Code]....

And this is the event that handles the delete command:

[Code]....