I can suggest that you try the following:
- Does upgrading to latest Telerik UI version helps - 2015.1.225?
- Can you ensure you are using .NET 45? I am asking about that because there is an issue in .NET4.0 related to IE11 detection. More information is available here - http://blogs.telerik.com/aspnet-ajax/posts/13-12-19/how-to-get-your-asp.net-application-working-in-ie11
- When does the issue occur - on page load or when a SocialShare button is clicked?
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