I tested it here on our test machine with the exact same parameters and it was working fine. Actually, the help has nothing to do with the Silverlight version.
This behavior is quite weird indeed. We have not experienced such a problem before. It might be something is wrong whit your Microsoft Document Explorer
that causes it to crash. Is this happening every time or just sometimes and is it happening only with RadProgressBar's help or with all topics? You can try to reinstall the Microsoft Document Explorer.
the Telerik team
Check out Telerik Trainer
, the state of the art learning tool for Telerik products.