Akai MPK49 MIDI problem (failure of MIDI on/off)

[CASPARBROWNE]

I recently bought an Akai MPK49. Its an awesome bit of gear and everything works wonderfully except 3 notes:

 

C1, C2 and A#.

 

With the MPK plugged in:

When i change the octave +/- the keys play perfectly so there is no problem with the actual keys.

 

With the MPK and K25 plugged in:

The strange thing is that when my MPK is plugged in alone, C1 and C2 do NOT work. But if i plug my Korg K25 midi controller into my mac as well, C1 and C2 work perfectly on my MPK but not on the Korg K25. While both controllers are plugged in, this is when A# works, but will not stop playing.

 

Personally i believe that something is up with the MIDI signal for those notes. i don't understand why plugging in another midi controller changes the problem.

 

Any help would be really appreciated.

Thanks.