I don't seem able to allow entry of negative numbers within the RadMaskedNumericInput. I've tried typing the number first and then pressing minus as suggested in other threads - ideally I'd like the users to be able to type the minus first though.
I've copied my very basic xaml below in the hope i'm missing something obvious! I can see that the demos work (although you have to type the number first and then press minus).
I'm using version 2012.2.607.1050 of the controls.