Logic Pro 9 How do you fix droning MIDI?

I know this is an issue that has a fix I just don't know what it is.
I'm running Logic 9 on a MacPro with a Mackie HUI & an M-Audio Axiom 61 with an M-audio MIDISPORT 2x2 making the connection to the mac.

So, if I"m working at home with Logic I have no issues...but the minute i bring the session to the studio, my instrument tracks start to drone if I dare select a track and hit a note.
The drone can be described as a pinging sonar at about 200 Hz.

I know there is something in the MIDI setup to correct this.
Anybody have a clue?

p.s. Logic also shares the Mac with Pro Tools HD3 Accel system. I use the same MIDI setup for it. I only launch one program at a time.
Sounds like an issue I was having that required me going to the environment window>clicks and ports>and deleting the cable from "sum" and creating a single cable connection from the midi port I was using.
figured it out!

My issue was in "Controllers."
I needed to set the Mackie HUI's Midi channel to its physical MIDI connection on the midisport 2 x 2 - in this case channel 1 ( in & out)
Once I did that all was fine.
thanks for the input! :)