Could you clarify a couple of points please.
In my case, a RadMaskedEditBox with the following settings:
.RadMaskedEditBox.MaskType = MaskType.Numeric
has a default value of 0. This is what I would expect as it only accepts numeric input.
If I change this to (e.g.) 44 and tab away, then the text still reads 44.
Is this what happens for you too?
For reference I am using the latest 2010 Q3 SP1 version.