I am afraid that the provide information is not enough for us to determine what the problem is and what exactly is your setup. In general, when closing RadWindow that shows a content page, you need to use the GetRadWindow() function to get a reference to the RadWindow object on the parent page. More information on the subject can be found here
If you still experience problems, please open a support ticket and send a sample project where the problem can be reproduced so we can check it.
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