Hi again Claudio,
There should not have been any breaking changes for the Manager.LaunchBrowser() method for SL 4. I just tested this out on the Telerik SL demos that are SL4 also and it seemed to work for me.
Did you uninstall the previous WebAii version before installing the latest version? And did your SL app load time increase with the upgrade? If so, please try increasing the Settings.SilverlightConnectTimeout to a larger interval.
Also, please see the attached SL connect document to see if anything mentioned in it applies to your app after the SL 4 upgrade.
All the best,
the Telerik team
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