Looking more closely at the logs, this appeared in my syslog when the bug manifested itself yesterday for the first time in eight days:
May 28 13:56:27 greengage kernel: [683758.866789] [drm:drm_mode_getfb] *ERROR* invalid framebuffer id -- [965g] Regression: monitor sometimes does not wake up from sleep https://bugs.launchpad.net/bugs/582938 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
