Internet Sharing Refuses to Function

I have a mac OSX 10.4.11 and used to use the internet sharing in order to let my ipod connect, and before it worked fine. Then all of a sudden it didn't work anymore. I would turn it on, the grey arrow would appear in the airport symbol, then it would disappear, and I wouldn't be able to connect. I have tried everything, absolutely everything, and I haven't gotten the slightest change.

I also noticed in my fury that there was no internet sharing tab to click in the services panel. But I don't remember needing to click that when it worked before.

What is going on? Please help, I've been trying to make this work for almost a month!!