Dumb question, but sometimes the simple things are forgotten. i use FC10 so i know a bit about your system but not totally familiar with it. On the network icon at the top in gnome panel networking is enabled? and you have checked (most commonly is) system eth0?
next question is your compputer set to a static IP or assigned by DHCP, make sure it lines up with your modem/router, your not setting a static to the same address as one already occupied?
Also check your OS firewall settings.
ping 127.0.0.1 see what returns. then ping 192.168.1.1 see what returns, also where is your DNS set to under network connections??
More info can make answering the question easier