Did a fresh install of Ubuntu 17.10 a few days ago on my Lenovo Thinkpad Edge (using an existing home directory on a different partition).
When I close the lid and put it to sleep, on waking it I can no longer login. Sometimes it spends ages checking the password, then says the password is wrong. Sometimes I can't even enter anything into the password box. To fix this I have to shut down and restart. Login always works fine on a restart.
The problem for me was CrashPlan keeping too many files open while I was away.
After rebooting, I looked in
/etc/log/syslogand found "No space left on device" errors around the time of my login failure. If you use CrashPlan and find similar messages, then this might work for you too. Messages like:
The instructions on the CrashPlan site worked for me (please read before trying on your system): https://support.code42.com/CrashPlan/4/Troubleshooting/Linux_real-time_file_watching_errors
Basically, as root I added this line at the end of
I'm grateful to this bug on launchpad for sending me to the CrashPlan solution: https://bugs.launchpad.net/ubuntu/+source/gdm3/+bug/1726996