I've got mythtv working with a keyboard now, but the builtin IR receiver and remote are sending signals to the keyboard and I'm not to good with trying to learn how to map the remote into the keyboard driver.  I managed to get the down arrow to map to a "D" and tell MythTV to accept "D" for the down event (this is possible in MythTV 0.19, but was not possible or at least not easy in previous versions).  But after the first D from the remote it starts sending repeated D events and the menu selector in MythTV just flys through the options repeatedly.  So I think I'm going to punt on the builtin receiver and hack up my own.  I can stuff a serial card in the 2nd PCI slot and attach a homebrew receiver to it, replacing the one in the front panel (if I can get the front panel off without breaking it).  I tried building homebrew IR receiver once before but didn't do too good a job.  But I should try again.  It is, after all, a pretty simply circuit to build .