Hello!
I think you don't have your default gateway well configured...
I am supposing that you have your computer connected to a router, and you are pinging your router... am I correct?!
If I am, just go to this thread and follow the recommendations :
http://www.linuxquestions.org/questi...hreadid=293615
If I am not.. just be more explicit... describe your system, and let's see what we can do for you...
See you
/edu