2 methods............
the easiest is to simply reboot, believe it or not.
the other way is to open a terminal as root, type..........
ps -aux (enter)
that will give you a list of all running processes. look for the PID number associated with any instance of urpmi, rpm, rpmdrake, &/or curl & kill them by typing........
kill (pid number here) (enter)
and don't stop installations or updates with ctrl+z anymore!
otis