The issue was related to a custom theme that I created based on Telerik theme . When I used the original theme , the issue fixed.
answered on 26 Apr 2012, 07:53 AM
I am glad that you managed to fix your issue. However, I just wanted to let you know that the RadNavigation has been obsolete for a while now. And this is why it will be better for you to update your code using the latest Silverlight navigation framework. The task is as easy as changing out classes with the built-in ones. You can read more about the Silverlight navigation here.
the Telerik team
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