One thing that I am curious to know is HOW are you attempting to connect? Are you using DHCP or static IP?
One thing to do would be to open a terminal, type su, provide the root password, and type ifconfig /eth0. Hit enter and you should be rewarded with information such as an IP address, subnet and the like.
Also, try the route commmand and see if your gateway (or router) ip address is present.
Once you have 1) an IP address, 2) subnet mask, 3)default gateway, and 4) a DNS address, you'll be able to get on the internet.
TIP: You may want to go to the system configuration in your GUI (like KDE or GNOME) and try to configure your network card that way. (it's 1000000000 xs easier)