When running the WCF / Windows Azure samples (see my previous blog entry) you may get an error indicating that the Polling Duplex Binding Element cannot be loaded if you have Silverlight v3.0 installed (The type ‘System.ServiceModel.Configuration.PollingDuplexElement, System.ServiceModel.PollingDuplex’ registered for extension ‘pollingDuplex’ could not be loaded).

Replace the reference in the WcfSamples project from the v2.0 Silverlight Duplex Polling assembly C:Program Files (x86)Microsoft SDKsSilverlightv2.0LibrariesServerSystem.ServiceModel.PollingDuplex.dll with the v3.0 version: C:Program Files (x86)Microsoft SDKsSilverlightv3.0LibrariesServerSystem.ServiceModel.PollingDuplex.dll

Set the Copy Local property to true.