The clue to the problem can be found here:
+ Downloading http://rell:1234/NewXbaps/WPFCarousel03.exe did not succeed.
+ The remote server returned an error: (415) UNSUPPORTED MEDIA TYPE.
* An exception occurred while determining trust. Following failure messages were detected:
+ User has refused to grant required permissions to the application.
It seems that your permissions or server configuration are incorrect.
This link could help you solve your problem: http://www.checkupdown.com/status/E415.html
the Telerik team