Cant connect to the internet

Hi,

I have a Mac OS X 10.6.8. And all of a sudden I cannot connect to the internet. My dorm mates can connect still, they can mac's as well. I have full bars of reception but I still cannot connect. I tried using the assistant thing in network preferences but that didn't work. I also tried deleting the Airport tab and remaking it. After I remade it, no IP adress and the circle turned yellow. Can anyone help? I need help ASAPPP

Thanks,

Adam