If everything else fails, and the correct DLL is deployed in the bin, try adding an assembly binding redirect in the web.config:
<dependentAssembly>
<assemblyIdentity name="Microsoft.WindowsAzure.ServiceRuntime" publicKeyToken="31bf3856ad364e35" />
<bindingRedirect oldVersion="2.0.0.0" newVersion="1.8.0.0" />
</dependentAssembly>
Change the binding version numbers as needed.