mpc 500 + e mu xboard 49 midi problem

hey everyone, I'm new to this forum, bought my 500 recently and so far I'm loving it.
I have a problem with it though : i can't get my emu xboard to send midi data to the mpc.

Here's the deal : my cables work (tested), the xboard works : if I plug it in another device, it responds.
The mpc midi in works : when I play with another midi keyboard plugged in it, it works flawlessly.
So everything works on its own, but not when I plug it together...
Soft thru is set to as track, ive tried other options with no success.

I don't know if it's a well known bug or something, but any help is very welcome!!!
Thanks,
Seb.

anyone ever had this problem or knows how to solve it? I can record midi from all the rest of my gear, but not from the xboard.
Yet the xboard can properly transmit midi to another piece of gear...
I'm completely lost here.