I would reach out to your cable/satellite provider. There are newer boxes that have come out that, for some reason or another, don't have the option to change to IR from RF because they need another cable. I suppose the cable converts the signal for you. They aren't common boxes, not by far, but I have run into a few in the past few months.
If they can't provide the cable, or the unit doesn't use one, they should be able to tell you exactly where to make this change, or even replace the current box with one that does have IR capabilities.
I hope this helps!
I just had a Bell PVR (and all the fixins') installed and I believe that this new PVR doesn't us infrared to control the PVR receiver (at least I don't see the normal glass for IR communications). Has anyone run into this problem and what I might be able to do about it?