Network Adapter Problem.

• boot to Mac OS, see if you can connect to internet (to make sure the adapter/ network cables are physically still good in condition)
  
• are there other computers that can access internet using the same router/modem? If there are, try switch the cables (to make sure the problem is specifically at the adapter)
  
• in Device Manager
   Spoiler
  

  right click [computer]> Property> Device Manager
  
  locate your network adapter > Property > Driver, try Roll Back Driver there;
  or, insert your Mac OS installation Disk and re-install Boot Camp there.