Wifi USB Adapter stops working intermittently

[Colin23erk]

Code:

colin@colin-NC110:~$ rfkill block wifi0
Bogus block argument 'wifi0'.
colin@colin-NC110:~$ ifdown wifi0
ifdown: failed to open lockfile /run/network/.ifstate.lock: Permission denied

As it failed I tried

Code:

colin@colin-NC110:~$ sudo ifdown wifi0
[sudo] password for colin:
ifdown: interface wifi0 not configured
colin@colin-NC110:~$

The Advent gets used when my friend comes so I would like it to be able to connect to You Tube