I had the same problem with my 2000 Quest. There is a site where they will give you the info on how to fix it (for a fee).
http://www.shareamemory.com/radio/in...m#volume%20fix
Now I don't know if there is a connection with this story I am about to tell.
My speedometer stopped working the other day. It also started to run very rough from time-to-time. I had my mechanic run a diognostic on the OBDII scanner. It said the speed sensor (no more speedometor cable these days) and the anti-knock sensor was in need of replacing. He reset the code for the computer on the vehicle. The speedometor works now and it runs fine without even replacing these parts. By the way, my radio display which hasn't worked for over a year suddenly works fine now.
Stay tuned. (no pun intended).