The problem is in the title. Here is the details of how it appeared:
Previous, 13.10 was fully working. I had my motherboard changed by DELL tech. the tech also reinstalled the original Windows 7, which crashed a month ago. As expected, Ubuntu did not boot after Win 7 was installed. I Downloaded a fresh ISO image of 13.10 and burned it on a DVD.
Re-installed 13.10 from this. At re-installation, it discovered a previous 13.10 and asked me what I wanted to do. I chose "try to repair". After repair, all the applications had gone (not a big deal). Mouse was working in the login screen but disappeared after login.
I unsuccessfully tried this:
gsettings set org.gnome.settings-daemon.plugins.cursor active false