When I hit Ctrl-Alt-Del, it logs me out to the login screen. It's supposed to bring up the task manager.
Turns out that "lxsession-default tasks" is the problem.
I searched, and there is almost nothing on the web about this command.
In Preference -> default apps for LXsession, I have set the default to Task Manager. But somehow it's not working.
Ubuntu 14.04 LTS, LXDE.
Find the entry that invokes "task manager", change the command from "lxsession-default tasks" to simply "lxtask".