14.04 - Keyboard does not work in login screen after sleep [duplicate]

I have an issue I'm not sure how to work out. On Ubuntu 14.04, after sleeping the keyboard will be non-responsive most of the time on the lightdm login screen. It's not completely non-responsive: I can still Ctrl+Alt+F1 into a virtual terminal to restart the lightdm service and everything is alright. However, obviously anything I left behind when I originally put the laptop to sleep has now been washed away, somewhat defeating the purpose.

Where do I look to figure out what the problem might be?

Edit:

As it turns out, the original solution I found does not solve the problem. It still recurs fairly frequently (without reinstalling the input package over and over again). In this case the mouse and keyboard work fine, except for typing a password into the box. This can be solved simply by highlighting some other GUI element, for example I click the power button in the top right. After that the text input works fine again. It's a bit bizarre...

Well, here's a solution that has seemed to work.

Keyboard and mouse unresponsive after suspend

sudo apt-get install --reinstall xserver-xorg-input-all

EDIT: This fix does not appear to completely work. See edit above.

I'm having the same issue, although reinstalling the xorg input packages didn't help. Dropping to the console and restarting lightdm does work, so that's a good temporary workaround. Hopefully a fix for lightdm will come soon. This has worked fine on the same laptop for Ubuntu 12 and 13 previously and only started after upgrading to 14.04.