Internet Sharing, from Ethernet through Airport

Hello, I have been using the Internet Sharing (IS) option to get wireless internet to other devices. It has worked well for the last month, however, recently it has had issues. Today is the second time I tried to set up the IS and it didn't work. Before this problem, when I would start the IS, a little upward arrow icon would show up in the airport. Now nothing happens; the airport is just on, but not transmitting anything. I have not changed any settings or done anything different whatsoever; both times it randomly turned off. The first time it took me a while to get it working again, but after just trying and retrying the same thing over and over, it eventually worked again. This time, I am having no luck. What could have gone wrong? My ethernet connection is working fine.