A running program has files open - If you delete a file
that is still open by a running program, the file disappears from
your directory, but is still kept alive by the system until closed.
Typically when this happens a file or files called .nfsXXXXX
will appear (use ls -a to see it) in your directory. If you
"rm" these files, they will magically reappear, since the program
is still running.
In this case, you need to look around at processes that might
still be running that are keeping the file open.
/usr/ucb/ps -aux | grep myusername
will show them to you. Use "kill" to kill them. "ps" will show
you the PID (process ID number) -- it's the first number after
the username. If, for instance, the PID was 22374, you'd use
kill -9 22374
("kill -9" means "kill this and I mean it". See "man kill" for more
information.) If you use remus and romulus, the offending process
might be on the other machine, so you may have to look on both
machines.