I am having a similar problem with my 990 as Dr. Z. The volume controls of both the 990 and my Harmony work fine as long as I don't have my IR emitter system connected and point them directly at the 990 itself. If I connect them and use the remote emitters, things go haywire. Either no response or no response and then a sudden increase or decrease in volume. Other controls seem to work fine on the 990 and my other devices are fine, too.

Outlaw has suggested I use Xantech's 794-10 with my current Xantech 791-44 to plug the IR directly into the 990 to avoid the IR signal bouncing around or whatever it's doing. Has anyone done this? Does it work?

I've tried just isolating the emitters signals from one device from the emitter in front of the 990 and that did not help, which surprised me.