Commented Unassigned: rendering issue when used with RegisterAsyncTask [28019]

The RegisterAsyncTask in Page_load calls the acx control using ContinueWith
The acx control contains CollapsiblePanelExtender.

This give the error:
Extender control 'cpe1' is not a registered extender control. Extender controls must be registered using RegisterExtenderControl() before calling RegisterScriptDescriptors().
Parameter name: extenderControl .

1. There is no error if I call the acx control without Continuation but this is ruled out.

2. There is no error if I remove the collapsePanelExtender from acx control and use it in continuation with async task .

Please let me know if any further information is required?

Comments: Sure thanks I will upload as sample project soon