In the upgrade wizard we do not list the version which is currently used in the project (the currently used version could be seen in the Configure wizard - right click on the project in the solution explorer and select RadControls for Silverlight -> Configure Project). That means that if the project uses .419 version when you start the upgrade wizard you will see only the rest of the version available on your machine. If the project uses version different from .419 than it will be listed when you start the upgrade wizard.
If this is not the case could you please send me the following information:
1. The version of the controls in the install location (navigate to the install location of the controls. By default this is C:\Program Files\Telerik\RadControls for Silverlight\Binaries\Silverlight\ and check the version of Telerik.Windows.Controls.dll - right click on it select Properties and lock for Product version in the Details tab). Give me all installed version if you have more than one.
2. The versions of the downloaded versions in the %appdata%\Telerik\Updates\
3. The version of the VSExtensions (In VS2010 select Tools -> Extension Manager, select the Telerik Silverlight VSExtensions and see the version on the right).
As for the Debug and Release configuration, they don't affect the versions in the upgrade wizard at all.
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