Had a minor problem with my Stock market platform. Set-up screen would freeze program. Called their tech support, got their "Linux guy", who advised remove all Java and replace, not with synaptic version, but newest Sun Java.

After removing, computer auto rebooted, and went to blue mem-test screen. Showed no errors, but couldn't get back in. Tried two versions of boot repair disc from iso (checked md5sum, showed good.), but fix aborted, giving apt-error detected. Opened a terminal and typed (or copy/paste): sudo chroot "/mnt/boot-sav/sda1" apt-get -f install.

My system is Ubuntu 12.04. Had a few very minor issues from install, all fixed. Also added some of my favorite gnome tricks just to make life easier, but none that could have caused this. Added script to add shortcuts to desktop, open terminal in any menu from inside it, access root terminal, etc. System was firewalled and using avast antivirus (o.k., I'm paranoid. Used to do Windows sys-op and security.) But relative newbie to Linux.