I tried the Mac/UA-1010 with my girlfriends MIDI enabled Piano and that worked fine.
So I then picked up another keyboard from my storage (a Nord Stage) and tried that - again fine!
I then went back to the original keyboard (a Korg Triton Studio) and I still couldn't get MIDI to pass from the Korg to the computer.
So it would like like a problem with the KORG - however, I then plugged the Korg's OUT into the Nord's IN and that DOES work?! So the socket isn't completely dead, just seems to not like the UA-1010 for some reason??
MBP 2.2 GHz Quad Core i7 8GB RAM OSX 10.7.2
Logic 9.1.6, MainStage2.1.3, Roland Octa Capture (UA-1010)