Been meaning to dig into WPF but that hadn't made it to front of the queue, which means when it comes to XAML I don't have a clue. Well, while checking out the samples for the Windows Speech API, I ran into an exception when starting a C# sample. The error message told me as much as "there's something wrong with this whole wad of XAML but I'm not going to say exactly what and where."
This sort of error is discussed here:
WPF trick: Debugging the XamlParseException
WPF: Debugging the XAML (continued) / Expression Blend training
Might as well start digging into this WPF/XAML stuff now.