USB flash drives not registering unless Thunar is running

[MR ZenWiz]

On one of my Xubuntu 14.04 machines, when I plug in a USB device, it
fails to mount or register unless I am running Thunar.  If I start
Thunar after inserting the device, I still have to click on the device
icon to have it show up (as in df, accessible from the command line,
in /media/<usr>/, etc.).

This only happens on my home desktop.  My work desktop and laptop have
no trouble with these.

I suspect it's a setting somewhere, but I have no idea which one.

I have done logouts, reboots, etc. and nothing seems to help.

TIA.
MR