Okay, I've installed the latest upsteam kernel (4.0.0-040000-generic) as instructed. It hasn't solved the issue. Also the link to the previous bug report was removed from my bug report, but this seems to contain useful information: https://bugs.launchpad.net/ubuntu/+source/xorg/+bug/1437051
Okay, I've installed the latest upsteam kernel (4.0.0- 040000- generic) as instructed. It hasn't solved the issue. Also the link to the previous bug report was removed from my bug report, but this seems to contain useful information: https:/ /bugs.launchpad .net/ubuntu/ +source/ xorg/+bug/ 1437051