I've been reading through the treads and have discovered a similar problem with my Tone Port KB37 — no sound. I've run the latest installers and have Logic Express. I feel like everything according to what I've read is set-ready. Here's the difference. The need in the level output isn't moving. I don't get  sound from iTunes, Logic Express or from my computer what so ever when the keyboard is plugged in. Here are some helpful specs:

Mac Laptop OS X version 10.5.8

Processor: 3.06 GHz Intel Core 2 Duo

Tons of memory, whatever.

Logic Express 8

Problem: Seeing this on start up: you have 1 Audio Unit(s) enabled which did not pass the Apple AU validation.

POD Farm ... Compatability ... Failed validation.

Hit Rescan and everything else seems to PASS.

Pod Farm 1.12

Again, if I unplug the keyboard from the USB port I can hear the previously created songs. Plug back in... silence.

What else could it be?

Sorry if this is redundant, I am not certain if it's the Tone Port or Logic or what.

Thanks!