Further to comment #38, what appears to be a permanent fix in my case at least.
I disconnected one of the three devices attached to the USB hub and rebooted Lucid. Problem remains.
I disconnected the second of the three devices attached to the USB hub and rebooted Lucid. Problem remains.
I disconnected the third of the three devices attached to the USB hub and rebooted Lucid. Problem disappears.
I reconnected all three devices attached to the USB hub (in different USB slots) and rebooted Lucid. No problem.
I powered off and rebooted a number of times. Problem has gone away.
It does still seem that the problem is related to USB. Might it be something to do with USB enumeration?
Further to comment #38, what appears to be a permanent fix in my case at least.
I disconnected one of the three devices attached to the USB hub and rebooted Lucid. Problem remains.
I disconnected the second of the three devices attached to the USB hub and rebooted Lucid. Problem remains.
I disconnected the third of the three devices attached to the USB hub and rebooted Lucid. Problem disappears.
I reconnected all three devices attached to the USB hub (in different USB slots) and rebooted Lucid. No problem.
I powered off and rebooted a number of times. Problem has gone away.
It does still seem that the problem is related to USB. Might it be something to do with USB enumeration?