A friend of mine's Karma is locking up. It starts up, does the spinning Rio thing, the HD spins up, then you can hear the HD click, and it locks up, with the progress bar not even halfway through the "K" in Karma. Then it restarts and does it all over again, until you hit Lock or do a paperclip reset.
Firmware was successfully updated to 1.68 and it's still doing it. I don't know what it was at before this. The "hitting" trick from Riovolution didn't do anything.