Alright, finally solved it! It was a web filtering program that someone had installed earlier.
Apparently it was blocking the CSS files from downloading. For some reason though, it was still working even though I had disabled all the startup items and 3rd party services. Of course, this also explains the weird 127.0.0.1 loopback errors as well, since the filter was redirecting all traffic through itself in order to do the filtering.
Thanks for all the suggestions.