Problem with IMAC internet connection!

Hello,
I have an iMac desktop that is about four years old and ever since I moved to a new house it cannot use the internet. My roommates macbook will connect and so does my pc laptop. We are using Comcast internet with a Netgear router. When I go to select our network in the network preferences window, it only lets it be selected for a couple of seconds, then it disappears. PLEASE HELP!! THANKS

Hello,
I just posted this in the hardware section but I think it probably belongs here instead. I have an imac desktop that is about four years old. After moving to a different apartment, it no longer connects to our wireless internet. My girlfriends macbook and my pc laptop will, however, connect. We use comcast internet with a netgear router. Also, the imac will connect to our neighbors internet. Any help would be great!
Thanks

I just reposted this in software, so please respond to it there. Thanks

You not only posted this twice, but posted it in the wrong forum both times! Duplicate posting causes confusion and clutters the forums. Also, please read forum descriptions prior to posting. If you feel you posted to the wrong forum, ask a moderator to move it for you. Don't post twice.