You can use the RadWindow and the RadAjaxPanel controls together and there should not be a problem with the appearance of the window inside the RadAjaxPanel. If you are opening the window with the radopen
function at an event of a control which causes postback most probably the problem you experience is due to the opened window disappearing after the postback as at every postback/callback the windows should be recreated. Please, find attached an example which demonstrates a scenario in which there is one visible on page load window, another one could be created by the Open window button which does not cause a postback and there is one Postback button which you can use to see how the second window will disappear after the postback.
Please, let us know if you need further assistance. We will be glad to help you.
the Telerik team
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