I have had ccfs where the Pronto forgot that one component was to get RF signals...but you say it looks like the RX77 is emitting IR.

If the signal is too weak, and you are using one of the double LEDs that comes with the 77, try a Xantech single LED (not a "blink" version, though). A single one will allow more current through than a double, and that might solve your problem.

Xantech Blink-IRs could be a problem, too; I think they are a visible LED in series with an IR LED, so they require more voltage. They might put out both visible and infrared light, but other manufacturers have told me that they behave differently from plain old IR LEDs.

Is it possible that the IR is already too strong? That is very rare, but I dealt today with turning up the IR output on an older Niles unit...we had to turn it down six years ago when we put in the Sony DSS receiver, but today it needs more IR for some reason.