Silverlight 4 Upgrade Breaks Silverlight Debugging Experience

A design change in the Silverlight 4 installer now causes older developer runtime to be upgraded when a newer client runtime installer is executed.  This causes the Silverlight debugging components to be uninstalled, and breaks the debugging experience:


The workaround for this is to install the latest Silverlight developer runtime, which you can find at

Sorry for the inconvenience; we’ll review this design decision for SL 5 and determine how to improve the experience.