Help please, Problem with OMS and Midisport 2x2 Options

[iowmike]

I would be grateful for any help ! I am trying to connect my Yamaha  PSR-225GM to my imac G3 using Midiman midisport 2x2.
Everytime I try to 'test studio' in OMS set up, I cannot get my Yamaha to be recognised (midi received). I am able to get the yamaha to play what seems random notes and sounds by clicking the mouse on the apprpriate icon. Any ideas as to why the mac won't 'play' when the yamaha keys are pressed ?
I've checked the connections, volume etc. and can't think of anything else.

[macmax]

GW just to note, when test studio is activated within OMS , a midi input signal should prompt OMS to 'say' midi recieved via the system 'voice'

IOWMIKE
could be something as stupid as a faulty midi cable. (seriously, this had me hunting for faults in my OMS setup for a week!!! before i thought to change all the cables. with 2 opcode studio 4s, >>> 16 Midi Input, and 16 midi ouput ports!!! plus thru boxes on 4 of them...<<< finding the duff cable was a bitch!)
Also the 2x2 is twin port, make sure the conections for the Yamaha are correctly defined as to which port it is sending to.
Also that the OMS'cable is intact in both directions...
Dumb i know, but i have occasionally come across someone who without realising , plugged the send to an output, coz some times its not all that clear which is which......
hope its of use
max