I have come across several instances of people having trouble using the new Reactive Extensions (v1.0.2.5) in projects that reference the Silverlight Toolkit (Nov09) due to the fact that the original release of the Rx Framework (v1.0.0.0) was bundled with the Toolkit. The trouble really becomes evident if you are using the Managed Extensibility Framework (MEF) to discover and compose portions of your application. Update: After getting some feedback in the comments, I was able to find a solution for...