Network icons showing not connected when my wired network cable shows that I am

view story

http://unix.stackexchange.com – One day the power just went off when was using my desktop computer running Linux 11.4. When later the power came back, I couldn't access the internet. When I open any browser, it tells me I have no connection. Even my desktop network icon shows that I am offline. But when I check the wired connection behind my desktop computer, it shows that I connected with a green blinking LED. What is going on with my desktop? All the computers in our lab are fine. Only mine which I use to administer our computer lab has this problem. (HowTos)