I have a bunch of custom classes (NumericTextBox and NumericConverter in this case) which I used successfully without any warning or error for a while. Now I just hit a problem where if I use the converter in the binding on the NumericTextBox inside a DataTemplate, the binding is broken. But if I use just the NumericTextBox or just the NumericConverter on its own or if I don't use them inside a DataTemplate, it all works as expected. I would like to have a clue what's going on!
Anyway you could download a test application there: http://www.galador.net/stuff/MysteriousBinding.zip
And what happenened is that the boxes circled in red in the picture below got no databinding for some mysterious reason, while all the other work fine!! The picture: http dev.agtrix.net/images.tmp/MysteriousBindingError.png (put the missing bit yourself, Stackoverflow won't let me post the link)