I tried this code and it seems to be working as expected - the URL loaded in the iframe contains the querystring parameter that is passed: http://screencast.com/t/0qclOIR43
. I am also attaching the page I tested with as a reference.
If your issue is on the server-side then this behavior should not be related to the RadWindow as it cannot modify your page in any way. Please try loading your page in a simple iframe and see if it makes a difference whether you pass the full URL or a relative URL. If it does - then this must be some browser quirk on the way URLs are passed to iframes, although this is the first time it is being reported.
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