If I've written the code to it, then I hook up the MIDI OUT jack to a midi capable device (in this case, MSSIAH) and it's powered by the wall jack and taking in data from the game boy, should I see a TX light?  Currently I'm not with that setup, unfortunately, and it doesn't seem to be feeding MIDI to MSSIAH. I have a loop running with each note having a Q00 command next to it to send that note as midi, which should do the trick if I understand correctly.

So I've got my Arduino Uno hooked up to my pc and the power brick hooked up from the arduinoboy to the wall, and I write the latest arduinoboy code to the board. It says it uploads just fine.  I test it out, sending midi via the midiout version of lsdj and the TX light blinks in time to the messages. Looks like everything is fine.

Then I unplug the USB cable from the Arduino, leaving the wall plug in place.  When I send midi messages to the board, the TX light no longer lights up.  I hit the reset button on the board, but  this doesn't seem to help at all. 

I had originally thought that this was a power issue, but since the board is being powered by the wall plug, there's no way it can be.  It's not an issue with the bad bootloader that the arduino Unos had previously- I returned a  faulty board with that issue to Sparkfun and this one they replaced it with works just fine with other Arduino sketches. After disconnecting and reconnecting power, the "blink" sketch keeps on working.

Anyone have any ideas as to what might be causing this?  The Arduinoboy doesn't rely on the Game Boy for power (I didn't include that pin in the link cable to the DMG since the last time I tried that it drained the DMG batteries like mad)

I'm using a slightly modified version of the arduinoboy code to default the arduinoboy into mode 6 (midiout). Is it possible something about that is screwing things up?