Midi Command Response. Help!

[dh187]

I am new to midi controlling. Sometimes Live will not accept the assignation of a midi command on the first few tries. This is often remedied by clicking out and back into the midi map mode. No big deal. The problem, however, is that sometimes Live will not respond to a midi command while it is playing when it is clearly receiving the signal. This is of course a big deal. I am using the bottom octave and a half of a technics keyboard always sending through the same midi channel to an 800mhz ibook via a presonus firestation. The problem seems so far to be very inconsistent. What should I know about the midi commanding situation in general? and what for my specific problems? Could it be the controller itself? Any ideas are welcome. Thanks.
dh187