OS X :: Piano Starts To Cut Out Playing Too Many Notes / MIDI Were Overloading Logic

I am running an M-Audio Keystation Pro 88 MIDI controller via USB into Logic Express 7. I use Mac OSX. I'm going straight from the Keystation Pro 88 into the MIDI port of my MacBook Pro. I use a Pre Sonus Firepod as my audio interface (not sure if that's even relevant...).

When I begin playing too many notes (especially after pressing the sustain), the piano (Garage Band grand piano .exs) starts to cut out. It sounds like BAD static, as if the MIDI were overloading Logic. I've tried changing the buffer size in audio preferences - it gets no better, only worse when I lower the size (32 being nothing but static).