Problem with Network

[usmansadiq_]

I am using ubuntu 8.04 and am new to it. The problem is, although I can connect to the internet through Firefox, I can not ping any computer on the network, nor can I use Host or nslookup. I have verified that my ethernet card is installed, and etc/network/interfaces contains its entry.

I just want to ask if its because of a firewall, and if its so, how can I unblock it. Moreover, please refer me to some good starting page to Linux Networking and Unblocking Proxy.

[superprash2003]

switch off firewall for sometime and then try.. if it works.. then firewall issue.. if not go to the terminal and type ifconfig and post output..which firewall do you use?