It's been a while since I used one, but from memory and from the manual:
Several things can easily trip you up on the MIDI settings on the O1V
On the MIDI set-up page (press MIDI button to get to page 1)
As mentioned, make sure you're on the same MIDI channel
(TX ch and RX ch, on the left side of the LCD panel)
Check to be sure that TX and RX are ON for Control Change and Program Change in the MIDI Setup panel (Program change recalls Scenes, Control Change is used for individual parameters such as on/off, fader level, etc for individual mixer channels)
Also, check the PORT setting to be sure it is set on MIDI and not HOST. (the "Link Port" will be set to the opposite of the Port - i.e, you should see "MIDI" under PORT and "HOST" under Link Port)
Also - check that the "ECHO" buttons are off for Program change and Control change, otherwise the MIDI message received on the input will be echoed to the output, which could cause some confusion with QLab receiving midi messages back.
There is a full table of Control Change parameters in the appendix of the manual (the manual is available in PDF from Yamaha's site)
Dave Tosti-Lane