My guess is that another assembly you are using is referencing the old dll. Are you familiar with all of the other project references being used and do any of them have a reference to the Telerik dlls?
Can you put in a binding redirect in your web.config file like this?
<dependentAssembly>
<assemblyIdentity name="Telerik" publicKeyToken="121fae78165ba3d4"/>
<bindingRedirect oldVersion="1.0.0.0" newVersion="2.0.0.0"/>
</dependentAssembly>