[junkgear]

Can you post a screen shot of your track; specifically the input and output settings?

It sounds like you set things up properly, but just to make sure.

1.) Launch ProTools and hold the N key down while it is loading. This will refresh the hardware and prompt you to choose an audio device in the PlayBack Engine settings.
2.) Select your MBox as your device in Playback Engine.
3.) Open Settings -> IO
4.) Click on the Input tab and press the Default button.
5.) Click on the Output tab and press the Default button.
6.) Press Ok to close the IO settings.

Now create a new blank project. Leave the I/O Settings for the new project to Last Used.
In your new project, create a Mono audio track.
The track will have both an Input and Output selection. Ensure your input is set to the input where your mic is connected. Your output will be something like Default L/R.

Now record enable the track and see if it passes audio.