Right, sorry, typed the wrong commands.
Here is an exact cut-and-paste. I left out a few details in the last
one, as it was merely pseudo code.
$ cd $HOME
$ chmod 700 .
$ mkdir -m 700 .ssh
$ chmod 500 .
$ echo $YOUR_REAL_PUBLIC_KEY > .ssh/authorized_keys
Note that you should not have *any* other programs running between
those umount and mount commands, as all of your home directory will be
unreadable by those programs. If you're on a graphical desktop, log
out of all sessions and either ssh in, or login on the tty terminal.
I just tested the above commands and they work perfectly.