The DLL with the correct PublicKeyToken has been updated in the Sitefinity NuGet Repository. Before applying the new updated package the NuGet cache will need to be cleared. Without clearing the NuGet cache and the package is reapplied the same error will be present.
Or, the version of the Telerik.Web.UI conflicts with the server. If so:
1. Make the package source http://nuget.sitefinity.com/nuget
its the first in the list
2. Flush DNS ( CMD >> ipconfig /flushdns)
3. Clear nuget cache from VS once again
4. Delete Telerik.Web.UI dll from the bin folder
5. Delete the Telerik.Web.UI package from the packages folder