Felix Miata suggested https://lists.debian.org/debian-user/2017/03/msg00895.html
Thanks, Felix, but I had already seen that and tried it, to no great effect. I should have said so. Except that I see the log I filed doesn't say so. Here is (part of) one that does, and fails similarly- [ 6651.505] X Protocol Version 11, Revision 0 [ 6651.505] Build Operating System: Linux 3.16.0-4-amd64 i686 Debian [ 6651.505] Current Operating System: Linux tresco 4.9.0-2-686-pae #1 SMP Debian 4.9.13-1 (2017-02-27) i686 [ 6651.505] Kernel command line: BOOT_IMAGE=/boot/vmlinuz-4.9.0-2-686-pae root=UUID=920046b5-b826-4c18-85a7-c986f9c15dfd ro quiet iomem=relaxed [ 6651.505] Build Date: 03 March 2017 03:15:35PM [ 6651.506] xorg-server 2:1.19.2-1 (https://www.debian.org/support) ... [ 6659.399] (EE) [ 6659.399] (EE) Backtrace: Apologies. Problem remains, however. -- Tony Stoneley, a...@ajms.ukfsn.org