Hi,
I have a page with two CollapsiblePanelExtender controls on it. The page is a multi-stage process which posts back to itself several times as the user steps through the process. All the page controls, includung the CollapsiblePanelExtenders are in an update panel and the page is derived from a master page.
When the page first loads, the CollapsiblePanelExtenders don't work properly - an open one will close on clicking, as epxected, but they only re-open intermittently and quickly reach a state where they won't re-open at all. However, once a user has initiated a postback by clicking on a form button, they work fine from there on in.
I can't work out what's causing this problem. Simply making the form post back to itself on load doesn't do anything, and neither does running the code that's initiated by the button click. I found - quite by accident - that inserting a StartupScript with an error (any error at all - just insert the the letter "a" in a script tag will do) into the page fixes the problem! But obviously that's not a satisfactory solution.
Can anyone shed any light on this? It's eating up hours of my time