I just switched from analog to digital cable.  I can still use my ATI 650 tuner by running the cable box output through it, but I obviously can't change channels without an IR receiver/emitter. I *hate* using typical IR remotes, and I really, really like my bluetooth Logitech DiNovo Mini keyboard I've been using up until this point to control my MCE pc. Is there such a thing as a cable that will go from a USB port (of my MCE pc) to the external IR input jack of my cable box that will be recognized and work with my MCE pc?

Doubt it.  You can use firewire to control the set top box if it has a port and drivers are available though.  See the FireSTB thread here on the green button.  I used to use this before getting a cableCARD.  The channel changing portion was 100% effective - the recording over firewire was about 50%.

Interesting, didn't know that was even an option, but it looks like the simplest solution. My STB's a  Motorola DCX3200 and it's got a firewire port on back, so I'll go to the office today and liberate a firewire cable and give it a shot.

SmoothMole

Doubt it.  You can use firewire to control the set top box if it has a port and drivers are available though.  See the FireSTB thread here on the green button.  I used to use this before getting a cableCARD.  The channel changing portion was 100% effective - the recording over firewire was about 50%.