Here is the code that I am using to load external web pages:
Page Name: BrowserPlugin.xaml
<telerik:RadHtmlPlaceholder x:Name="radPluginHolder" RespectSilverlightLayoutMeasure="True"
url = new Uri(Params["_RequestedPage"], UriKind.RelativeOrAbsolute);
radPluginHolder.SourceUrl = url;
Params["_RequestedPage"] will have the external page URL. When I load BrowserPlugin.xaml inside a RadTabItem the web page is not getting loaded inside the RadHtmlPlaceHolder but instead it is throwing the Silverlight application and loading inside the IE browser. I remember this was working OK when I used Silverlight 2 controls but now it is behaving differently.
Interestingly, I notice that this behavior is random. Sometimes all pages are loaded inside the placeholder but suddently the behavior changes and loads the page inside the browser and removes my silverlight application. As a sample, I loaded http://www.google.com/ and http://www.cnn.com/ . When I try clicking the links they open inside the placeholder and inside my tab control and everything looks fine. But if I keep clicking those links several times then suddently the behavior changes. I would say 4 out of 10 times it behaves incorrectly.
Please let me know if you need any further details.
Thanks for your help on this.