Turn down the hardware buffer size down to 128 samples or 256 samples, dependin on what you're computer can handle. you'll probably find that once you start mixing, PT wil require you to increase the buffer size. But for recording, get it as low as possible.
Also, the "mix" knob on your M-box lets you select how much of the microphone input and how much of the PT output you're hearing, so if you set it mostly to the mic you'll lessen the latency problem.