dual monitor config -- used to work -- now broken

I have a configuration that, until this morning, was working – at least sort of. I have a laptop with 1024x768 resolution and an external monitor with 1280x1024 resolution. Previously, I had it configured I could use dual monitor mode, although part of the 1280 x 1024 spilled over onto the laptop monitor (external to the left of laptop).

Last night, I undocked the laptop, after setting config to mirror at 1024x768. This morning when I try to set it back, using the ‘display configuration settings’ I cannot get dual mode to work. It reports:
Method “ApplyConfiguration” with signature “” on interface “org.gnome.SettingsDaemon.XRANDR” doesn’t exist

other messages include: ‘reported failure but didn’t set the error’ – paraphrased.

I assume that some update broke it. Does anyone know how to a) make it work, or b) undo the update?



The other error message was: “Method invoked for ApplyConfiguration returned FALSE but did not set error”