Volumio system commands not working

Hi, I have Raspberry Pi B+ running Volumio v1.55 with an attached external USB drive holding my audio. I tried to attached a NAS drive via the Volumio web interface, but since I’ve been unable to do this a number of system commands from the Volumio web interface have also stopped working e.g. ‘shutdown’, ‘reboot’ and ‘remove NAS device’. I can still play music as previously and ‘puTTY’ to the Pi from a PC and use the appropriate UNIX commands to shutdown the PI. Also I can sync my music stored on a PC with the Pi using ‘sync toy’ so the network is OK. Any advice before I re-image the SD card and start again? Thanks in anticipation.