This can happen, sometimes fixed by re-installing VS or installing VS 2008 SP1. In this case it seems Javascript breakpoints do not seem to work in Visual Studio 2008 when Silverlight debugging is enabled, if you un-check the Silverlight option in the debuggers section, the JavaScript breakpoint will now be hit. Not sure if it's by design or a bug...
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In code behind for WPF/Silverlight in Visual Studio you can use the key combination snippet (assuming defaults) ctrl-k then x then NetFX30 then either choose either a DependencyProperty or attached DependencyProperty.
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