Suddenly, Orange is ignoring my stylesheet?!?

I clicked on something in the Theme tab, and all of the sudden Orange has begun to ignore most of my stylesheet instructions. I don't use a separate stylesheet, so the only choices in the Stylesheet dropdown are (Default) and LightComic.css. LightComic.css changes to that stylesheet, but when I change back to (Default), I'd expect it to use the CSS data from my .DAX file - but it doesn't. Any idea what I've done and how I can undo it?

Make sure that there are no DAX errors in the CSS section of the template.

If error occurs in the CSS section, you will not see any error message, but entire stylesheet will be ignored. Most typical error that may occur is reference to variable that's not properly declared in Declarations section.

Andrei