Joe,
I've found an issue with the CSS hander when a CSS property has more than one URL in it, such as a @font-face declaration or multiple backgrounds. The first occurring URL gets the correct path, but the others are ignored. Here's an example:
@font-face {
font-family: 'Glyphicons Halflings';
src: url('/Data/Sites/1/skins/micromo-mobile-dev/fonts/glyphicons-halflings-regular.eot');
src: url('/Data/Sites/1/skins/micromo-mobile-dev/fonts/glyphicons-halflings-regular.eot?#iefix') format('embedded-opentype'), url('fonts/glyphicons-halflings-regular.woff') format('woff'), url('fonts/glyphicons-halflings-regular.ttf') format('truetype'), url('fonts/glyphicons-halflings-regular.svg#glyphicons-halflingsregular') format('svg');
}
This can cause some pretty big issues as you can see, I hope you can fix it easily.
Thanks,
-Elijah