Comment # 21 on bug 1176734 from Ralf Gerhauser

After doing
  # service NetworkManager stop
  # systemctl stop wpa_supplicant
and testing the two configurations, I tried to re-activate NetworkManager. 
This works fine for wired connection eth0, but no more for wlan0.

When I try to re-enable WLAN AP (as before), nothing happens.  A reboot did not
help, the problem persists!

# nmcli connection show
NAME            UUID                                  TYPE      DEVICE 
Wired Ethernet  a07d7208-0987-4924-9394-2d362889cd6e  ethernet  eth0   
linux42-wlan    50a70604-cd83-4d0c-ab68-f61712f741c6  wifi      --     

# nmcli connection up id linux42-wlan
Error: Connection activation failed: No suitable device found for this
connection (device wlan0 not available because device is not available).

# rfkill 
ID TYPE DEVICE      SOFT      HARD
 0 wlan phy0   unblocked unblocked

# iwconfig wlan0
wlan0     IEEE 802.11  ESSID:off/any  
          Mode:Managed  Access Point: Not-Associated   Tx-Power=20 dBm   
          Retry short limit:7   RTS thr=2347 B   Fragment thr:off
          Encryption key:off
          Power Management:off

Any idea what's gone wrong?