My local cable guy delivered 3 of these brand spanking new RNG-110 boxes [ www.comcast.com/corporate/customers/customer_support/digitalsettopbox.html] (box is at the very bottom of the page) to the jobsite yesterday and I'm hoping I can swap them for older boxes... we've been getting the Motorola DCH-3200 for a couple years. He seems to think the new boxes are the bomb, though; while I was noticing the smaller rack-unfriendly shape, loss of coaxial digital audio output, and curved front IR window. 

I found a RNG-200 codeset in the MX-900 editor that turned the power on & off, so I thought I might be good to go. Hooked up the MRF-350 base station, put an emitter on the cable box (the IR window is also the site of a row of 4 colored status leds), and mono 1/8" cable into the rear IR input of an Integra receiver.

Got upstairs to the TV -- and no control of the cable box whatsoever. Volume, Power, etc on the receiver works just fine. Just for kicks, I swapped the emitter and mono cable to see if the "IR Receive" port on the back of the cable box was active, and--big surprise--it wasn't. Back to the emitter. I increased and decreased flasher brightness and got no response. Held the emitter over various spots on the IR window to see if there was a sweet spot, but couldn't find any place where the flasher worked.

If I point the MX-900 at the darn box the "Remote" LED lights up every time.

At this point I'm wondering if the row of LEDs on the cable box is blocking or interfering with the flasher... The manual (see link above) indicates a possible "front panel brightness" setting. Hmmm.

The base station ID is set to "E"; I'm going to switch that flasher to RF only and assign it a specific port in the morning ... by which I mean the afternoon, assuming things get done. May also try a non-URC IR emitter.

Wonder if anyone else has wanted to beat this box into pieces with a hammer.