While flying a training mission I noticed that the Master Arm switch was in the armed position but the MFD indicated weapons Safe. I tried resetting it with my HOTAS, keyboard to no avail. On checking in Free Flight the same problem occurred. I then tested the Master Arm with the A-10 and it worked perfectly. So it would appear to be a problem with my F-18. I also uninstalled and reinstalled the Hornet but the problem remains. Can anyone help