Have you tried to move your CSS up to the CSS folder and not in a CSS\appname folder?
I thought I read a long time ago (when the beta was 1st released, that you no longer need an app specific folder (of course you might want to put your graphic resources in one, to not overlap!). That instead, all of your CSS in in that folder, and any Javascript is in a JS folder.
Notice that the Custom\CSS folder comes with a northwind and a style.css
Bruce