Mbox 2 Mini: output is okay but inputs don't work

[Tarktones]

I am on a late 2009 MacBook Pro running 10.6.4, just installed Pro Tools 8.0.3 (clean install; this computer has never run Pro Tools before) and I can play back audio from ProTools or iTunes with no issues at all. However I can't get any audio from the Mbox into the system.

If I record arm a track in PT the meter jumps most of the way up and holds there (as if it's in a feedback loop or something) but there is no actual sound that passes to the output of the application.

If I open up Amplitube 2 in standalone mode I get the same behavior no matter what I set the sample rate or buffer to, the input meter pegs but I get no actual audio out of the program.

In either case if I turn the "mix" knob to the left I can hear the incoming audio just as I'd expect (this is with a microphone in Ch 1 or a guitar plugged into the DI on either channel). I know I haven't gone through any in-depth troubleshooting yet but I was hoping someone might have a good idea as far as where to start. Hopefully I'll be able to test it out at a buddy's place to see if it's an issue with the Mbox hardware.

[AdamPT8]

For some reason this happens from time to time, make sure you have Pro Tools updated, since the latest update 8.0.4 it hasn't happened to me. When it did used to happen it was a case of restarting PT a couple times until it worked.

[Tarktones]

Thanks for the reply, Adam. I'll try the update and playing with restarting PT a few times and see if I can get any results.