I just got my new Akai MPD24 talking to the transport of Pro Tools 8. It's plugged into the PC via USB. The first thing I did was update the MPD24 to the 1.10 firmware (the latest).
Setup->MIDI->MIDI Studio Setup
I created the MPD24 as a Akai MPC2000, Input Port = USB Audio Device, Output Port = USB Audio Device [Emulated]
Setup->Peripherals - Machine Control tab
Enable MIDI Machine Control Remote (slave) and leave it set to 127.
