I've just switched from os 9 to os X, AND got my first MIDI controller, AND my first synth software, (Reason 2.0).
Therefore it's not really surprising that I'm in over my head but... well, it SEEMED like I knew what I was doing.
Audio MIDI Setup can see the Edirol PCR-50, and Reason can play it's own songs internally, but I cant get any sound
from the keys to the program. I think it has something to do with which channels are transmitting...maybe?
Any insight on this matter would be incredibly welcome!

And I THINK it's be more appropriate in the OS X forum.

My advice is to check the channels on the controller and in Reason. And also to look at the Midi control panel. Sorry not to be able to tell you more, but I'm not on OS X myself.

I have a recurring problem with my Oxygen 8, which is that when I create a new instrument the cables aren't always connected round the back in Reason. I have to do it manually (click and drag the mouse from the instrument's Out to the Mixer's In) but it always works.

And this is possibly a stupid question, but have you selected the PCR-50 in Reason's Midi Preferences?

As for Midi channels, I think they're automatically selected, but if not just do that. Select the instrument's channel in Reason (the little arrow pull-down box by the instrument's name on the left-hand side of the sequencer) and then click to the far left of this area to make the Midi icon appear for this track. Then select the same channel on your PCR-50 and you should be in like Flynn.

If not, I'm fresh out of ideas.