Hi there, I*m exactly having the same problem:
I can't use Ctrl + + (Num Pad) as indicated here http://wiki.jriver.com/index.php/Keyboard_Hot-keys for Volume down as there is no num pad in the GUI software.
Using Ctrl + = as an alternative programs the FLIRC to return Ctrl + alt + @
Using Ctrl + - (Volume down) will program the FLIRC to return nothing.
I tried it serveral times. Also restarting the GUI software, clearing the buttons or Clear Configurations.
Thanks in advance. Your help will be much appreciated.