I/O error on two devices

I'm on Calibre 7.15.0 which I reverted to after having problems with the most recent F/W.
This morning, I had an IOerror problem when trying to send new books to my Sage (no problem connecting or upgrading reading positions). I suspected a data base problem, so I tried with my Libra 2, which I have not used since I last synchronized it with the Sage (3 August), but I have an IOerror immediately on connection. I exited Calibre and tried again with the same results.

Libra 2
calibre, version 7.15.0
IOError: disk I/O error

Traceback (most recent call last):
File "calibre\gui2\device.py", line 112, in run
File "calibre\gui2\device.py", line 566, in _books
File "calibre\devices\kobo\driver.py", line 2049, in books
File "C:\t\t\apsw-42s16m2x\src\cursor.c", line 240, in resetcursor
apsw.IOError: IOError: disk I/O error

I don't see how it could be a database error on both devices, one unused. Does somebody have an inkling what the cause might be?

EDIT: precisions on the moment the IOerror was signaled.