I've seen some discussion of this issue, but nothing definitive.
When using a USB hub with MIDI devices, Max correctly discovers all devices and their port names, but when I use one of those port names in a MIDI "in" object of any kind, all communication ceases. i.e. if I leave the MIDI object with no port specification I get MIDI input, if I specify a port by a name provided by midiinfo, or by an abbreviation letter, I no longer receive data from that MIDI object.
Is there any hope that this can resolved, or is it a limitation of USB, or possibly just my USB hub?