(k, replied a bit on lines, but better keeping it here)
the only issue I had with hot plugging, was if NO other device was plugged into the hub, the hub doesn't come out of power saving mode correctly... and subsequently, throws all sorts of weird errors.
so plug anything (usb drive, midi controller) into the hub, then boot bela,
then try plugging the monome once the boot is complete.
(actually, I think its also ok, if you plug in the hub with the device (e.g. monome), after its booted, but cant remember for certain... so best to try this, once we have more info)
it would be good if you could post what your seeing from the console logs (dmesg), something should appear there even if the device is not recognised.
as also mentioned on lines, what Id also try, is running on the current BBB distro, and seeing if it works there... as its got a newer kernel.
(what I do , is run Xenomai/bela off the sdcard, but have the current bbb distro in emmc... useful for testing things )