No halt/poweroff on an EliteBook 840 G1 after upgrade

[Miguel Ortiz Lombardía <miguel.ortizlombardia@laposte.net>]

Hi,

I'm running Debian testing (jessie) on an HP EliteBook 840 G1 laptop.
Everything goes reasonably well, even very well, except that after
running apt-get update/upgrade on Monday (15 December) I cannot halt
(poweroff) the computer. When I try to switch it off it just reboots. I
manage to get it in sleep mode by pressing the the physical start button
and this is what I'm doing since then. No previous problems in this
sense before that upgrade. I have 'intel-microcode' and
'firmware-linux-free' installed from the beginning.

Anyone experiencing the same problem or having an idea about how to
solve it?

Thank you!
Cheers,

   Miguel