I wrote up a page about my issue here: http://wiki.dprogramming.com/Dfl/Dmd0161 where the issue is "using with(expr) where expr has overridden members you are using [in the with body]" and the error is caused in the example because Label.text overrides the base Control.text.

I'm not sure if it's a bug or a feature, but it looks like it may cause many issues.