I also have a Motu 828 on my computer, so I had a peak: thanks Patrick, you're quite right, and the faders are down there too, but I get sound in and out, so obviously the faders greyed out and down is not the reason why I'm getting no audio into max on theother computer.
The other computer, a mac mini, is not mine, but since the guy bought it because I told him my software would be better for him than a hardware phrase sampler, I feel sort of obliged to get this sorted for him :-)
As it is an Alesis interface...
I recently tried during a couple of hours an Alesis photonX25 with a
Mac (OSX.3.9 and OSX.4). I first had no sound neither, until I changed
the vector sizes in Max/MSP (I don't remembered what I did, I just
changed the settings a couple of times, for both signal and i/o
vectors). I must admit that I didn't try this interface with other
software than Max/Msp (even not the Finder).