A new feature in Microsoft Silverlight 4 version 4.0.60129.0 improves HTTP stack latency and improves network latency by up to 90 percent. This feature is designed for applications that are built for the 4.0.60129.0 runtime version of Silverlight. To use this feature, update your application to require the 4.0.60129.0 runtime version of Silverlight.
How to change the required runtime version of your application in a development environment
To change the version for your development environment, edit the ReferenceAssemblies registry key.
To do this, follow these steps:
Open Registry Editor and locate the following registry key: