Sorry to barge in here as I'm not an Omni user (yet). I am experiencing the same exact problem on these Gawker sites with each browser on my system (Firefox, Camino and Safari - all the latest builds) I've removed all firewalls and still no style sheet. Very perplexing.

edit to add:
DL'ed Omni (unlicensed); adding the suggested amendments to the white list and still no style sheet. >.<