Had same problem with a clients Inspiron 15R.
Connected to wired or wireless but no data.
Opened McAfee - it had updated and was waiting a McAfee instigated reboot. OK'd reboot and all good.
Guessing McAfee must have blocked the network ports whilst waiting a McAfee instigated reboot and for some reason didn't communicate the need for a reboot to the OS (Win8)