Sys.WebForms.PageRequestManagerServerErrorException: SetPartialRenderingMode can only be called once

Hi All

this is in usercontrol. And this usercontrol is the part of SharePoint WebPart

When I click ajax:CollapsiblePanelExtender it throws above error

Sys.WebForms.PageRequestManagerServerErrorException: SetPartialRenderingMode can only be called once

<ajax:CollapsiblePanelExtenderID="CollapsiblePanelExtender1"runat="server"TargetControlID="pnlIssuesControls"CollapseControlID="ImgButton"ExpandControlID

="ImgButton"