When opening a RadWindow from within another RadWindow I would generally advise that you actually open it from the parent page, as shown in this help article: http://www.telerik.com/help/aspnet-ajax/window-programming-opening-from-within-dialog.html
. In this way the second one is not confined in the first.
On a side note - I would advise that you upgrade to the latest version, since many fixes and improvements have been made for the past two years and also IE9 support was added in Q1 2011.
All the best,
the Telerik team
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