I am assuming either USB or Ethernet is what you mean by "cable" and this would be saying work offline because no internet connection, so first suggestion is
Turn Laptop off
Turn Internet modem off at the plug
Put Usb/Ethernet into the laptop and make sure is DEFFO connected in both Laptop and Modem, and turn laptop and modem on at same time, so usb or ethernet is plugged in before turning laptop on because sometimes if just plugged in once loaded ect it won't work and after doing this you will find out if that's what your problem is.
IF NOT WORKING ONCE TRIED THIS, INCLUDE MUCH MORE DETAIL IF YOU HOPE TO SORT THIS OUT
Simon, April 2010