WPF ValidationRule bug? Backspace is ignored. Is there a work around for this?

My work mate is having this problem as well, we haven't had a chance to do much in the way of investigation.

Steps that reproduce the problem in a textbox in a datagrid with a validation rule attached.

1. Enter some illegal content in such a way that one backspace should return you to legal content.
2. Hit back space - the text box is still showing an error when it shouldn't be
3. Hit backspace again and the error clears

Has anyone come across this and know of a work around?

T开发者_如何学Gohanks in advance!