Richard,... i just spoke with Samuel, he is a brazilian guy here.
What he did found, is with a HES CIB (old guys) USB connected directly on the MacMini, from time to time, MacMini freezes.
He also figure out, with a ArtNet device interface, that problem did not happened again.
Any clues if that happens before. I particulary still have 2 Cats with CIBs and no problem so far. Sometimes on the opening of the software does not read the CIB, but a computer restart solves and goes fine from there.
So any clues on CIBs and Macminis or so ???