Keyboard and mouse lock when switching to HDMI Input

[conomc]

Over the last couple of days I have started to encounter an issue with my HP ENVY Curved All-in-one.  I am working from home using a laptop which is plugged into the HDMI Input of the HP machine.  I can switch from the HP desktop to view my laptop using the same <Ctrl>-<Shift>-S-D "salute" as I have been using for the last year or more.  However I no longer seem to be able to switch back by repeating the command.  The only way I can get back to the HP desktop is by unplugging the external HDMI connection and waiting for the system to notice there is no external signal.  When I return to the HP desktop, my keyboard and mouse are unresponsive in Windows EXCEPT I can get <Ctrl>-<Alt>-Delete to work.  On Windows 10 this takes me away from the desktop to another screen that offers a few options including Lock, Sign Out, Task Manager amongst others.  The mouse and keyboard are responsive on this screen, so my problem is not a hardware fault on the input devices, or a USB dropout.

When I bring up Task Manager from this screen I can see that the HP Display Control is running with high CPU.  In the desktop the keyboard and mouse are unresponsive again so I'm unable to delve further into what is going on.  I can restore responsiveness by signing out (from the aforementioned screen) and then signing in again.  At that point all is back to normal, until I switch to display the HDMI Input when the whole thing happens again.

My suspicion is that is related to a recent Windows 10 update, but I can't prove that.  Is anyone else seeing this behaviour?  Any suggestions about how to fix it?

Thanks

Conor

[conomc]

And.....now it is fixed.

I installed the BIOS update (which also involved a reboot) and now everything has gone back to normal.  Not sure if the BIOS or the reboot was responsible, but felt I should post here just in case anyone else sees the same issue.  I hope to never see it again, but if you do and work out a definitive fix please post below.