Might be a USB Host scheduler bug, indicating that something wanted to talk to a USB device, but the kernel thought it didn't have enough of the 12 Mbit/sec (or 480 Mbit/sec in USB2.0 HS, or something GBit/sec in SuperSpeed, etc.) bus to satisfy the request.
This got me thinking and I tried it again on the laptop that has a USB 3.0 port. I tried it directly in that port (no hub), although I DID use a USB 3.0 extension cable. It works!
So the problem (at least on this laptop), is that it needed the USB 3.0 port? I thought that it was supposed to work on any USB port? *shrug* It doesn't appear to work on the cheapo amazon USB hub that is plugged into a different USB port (but I can't say for sure that that port is USB 3.0 or not, though).
Thanks for the tips! Regardless of what was wrong, it's working now!
--Roy K3RLD