Help With Mbox, Can't figure this d@mn thing out... Options

[The Iguana]

My History:
I originally started recording using an M-Audio Quattro interface and Audacity. However, I soon wanted to graduate to larger projects and all of my friend use Pro Tools, so I bought an Mbox. So far, it's been great, but I'm running into a major roadblock.

My Setup:
20 channel mixer.
Mbox outputs 1 & 2 go to mixer inputs 19 & 20.
Mixer's Aux Send 1 goes to POD Pro line input 1.
POD Pro stereo output comes in on mixer channels 4 & 5.
Alt Group outputs 1 & 2 go to Mbox inputs 1 & 2.

The Problem:
You get the idea. I bring everything into the mixer on it's own channel to audition. Then, when I'm ready to record, I punch the track over to Alt Group which sends it to the inputs of the Mbox. Record into the Mac, no problem. Then, I can bring the outputs of the Mbox in as a channel to play along with. All is cool.

The issue is when I want to process something previously recorded through the POD Pro. If I hit play on Pro Tools, it goes out through the Mbox and into the mixer. I send that aux of that channel to the POD Pro, then punch the POD's channels into Alt Group. This should allow me to play my track, process it outside the Mac, and record the results into another track. The problem is that this isn't working. Whenever the Mbox's channel is punched into Alt Group, the meters fire up, but Pro Tools shows nothing on it's input meters, and when I record, I get nothing.

The only thing I can figure out is the Mix knob on the Mbox. According to the docs, this adjusts the amount of input or playback signal in the output mix. Since my output ultimately becomes my input again, I don't want to setup a feedback loop, so I turn it all the way to "playback." However, when I do this, Pro Tools gets no input. According to the docs, the knob has no effect on input signals. But why can't I record? I can punch any other channel into Alt Group and get a nice clean track. Why doesn't the Mbox's track come through? Plus, how could it even KNOW?

HELP!