Hi Hendrik Klompmaker,
Telerik RadMediaPlayer is built on top of the default MediaElement in Silverlight 2. Since the standard MediaElement in SL does not prompt for credenatials, neither will RadMediaPlayer. RadMediaPlayer does not extend the behavior of the MediaElement in terms of Straem Authorization, yet. Nevertheless, we will surely research the matter and once we find the best approach we will implement it in the control.
the Telerik team
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