Flashing Amber!

Ahh... as some of you may remember i posted on here a while ago about a problem i had with the internet sharing on my windows and my mac. my mac got internet, but my windows box didn't. i had a friend of mine come over who knows nothing about apple and hates them for some reason and he fixed the internet on the wondows box. yes, right? wrong. now the internet wokrs on the windows but not on the mac. the airport wont recognise the internet connection and is flashing amber. everything is plugged in and basically I need help. so please help.

Can you see the network on your mac? There's a "baseball diamond"-shaped icon on the upper right task bar. Your buddy may have encrypted the network using WEP or WPA encryption (which is a good thing) and you would type in this key in the "internet connect" dropdown below this icon.