I have been using Ubuntu for the last 7 years or more but this one has me stumped. I am getting the dialog in the attached photo after misguidedly booting into Windows 8.1 and running the security updates there. I have a dual boot system with Ubuntu 14.10 and Windows 8 on a 2tB disk, Ubuntu 14.10 and Windows 8 readonly on my old 1tB disk which is also running. I have a 1 tB External drive for backups.
Previously I was successful in getting the system to boot after troubles when upgrading to Ubuntu 14.10