uslcom drops chars(?) when used with hub

[Steve Franks]

After my last 8-stable buildworld, I can't upgrade firmware on uslcom
devices plugged into a hub.  I can still talk to them over a terminal,
but it seems anything that slams bits at them 'fast' dies an early
death.  Works fine in motherboard usb slot, however.  Also, had
identical hub that's rarely ever used, which has same behavior, so all
things point to an OS/quirks type issue.

How do I even begin debugging this?  This is a major problem for my
day to day workflow.  I do *a lot* of firmware upgrades.

Steve