Hello Brian,
I am not quite sure if this problem is related to the RadWindow control. If I understand your setup correctly, you are loading an external page (different from the parent one) in the RadWindow and then you call Response.Redirect() in the context of the content page, is this so? In such case what happens if you don't use a RadWindow but display the content page in a standard IFRAME?
Greetings,
Georgi Tunev
the Telerik team