Vexing rewire~ problem.

I've been working on a MAX patch which does a number of things to control Reason, and have been developing it on my laptop, which works fine. I copied the files over to my desktop (both OS X), and rewire~ doesn't appear to be behaving. When I attempt to start the patch, I get "error: ad_rewire: error starting audio. Is ReWire mixer running?"

I whipped up a cheesy "test patch" for this problem, and sure enough, it works on the laptop, but not on the desktop. I checked the midi settings, the appear to be the same. Reason reports it's running in slave mode.

Here's the test patch:

I just run something in reason that perpetually makes noise (two subtractors wired with the lfo out on one running into the gate on the other) to see that it's working.

Any ideas? Seen this problem before and know how to fix it?