I have several pages that have a .NET UpdatePanel within which is a RadTabStrip controlling a .NET MultiView control via the OnTabClick event. The behaviour we were seeing was that after clicking the RadTabStrip and having the MultiView change views, most controls on the page because unresponsive. Clicking on a "blank" space within the page would then allow the controls to respond. The most obvious case was a dropdownlist that, when clicked, would get focus but not actually drop down to display its items. If we clicked on a non-control area of the screen then clicked back on the dropdownlist, it would then drop down and display its items.
I did a number of experiments, including changing the MultiView over to a Telerik MultiPage control. If I did this and set the MultiPageID in the RadTabStrip and removed the firing of the OnTabClick event, the problem behaviour would not occur. But we need the OnTabClick event to initialize controls within Views/Pages.
If I removed the top-level UpdatePanel containing the RadTabStrip and the MultiView, the problem would not occur. However, then we would have an undesirable full postback.
If I put an UpdatePanel around the MultiView and set the RadTabStrip as an AsyncPostBackTrigger, the problem still occurred. If I changed the trigger to a PostBackTrigger, the problem did not occur but again we'd have the undesirable postback page "flash".
I found that one page we had did not experience this issue. The difference was that all controls on the page (except for a RadWindowManager, which was declared before the UpdatePanel on all pages concerned) were contained in the ContentTemplate of this "top-level" UpdatePanel. The problem pages had divs containing controls and additional UpdatePanels declared after/outside of the first "top-level" UpdatePanel.
Moving these divs/controls/update panels inside the top-level update panel eliminated the error. After clicking the RadTabStrip and having the MultiViewchange views, the page controls responded to input. For example, the dropdownlist described above correctly dropped-down and displayed its items when clicked.
Any ideas what exactly is going on with this? As far as I can tell, I'm able to move everything into the top-level update panel without breaking my pages, but I still don't know exactly WHY that solution works. I can't easily post a code example since there's a lot going on in these pages. If necessary I can try to create a sample project that reproduces the issue.