it should run "after all other init scripts"..that read somewhere. perhaps in it's manpage..anyway, you can test if it works by adding there a line (in the rc.local file) that creates some empty file...like
now next time you reboot, this is what happens: if the rc.local is read and run, you'll get a file called "worked" in your /home/username/ directory (replace username with your login username) - if the script isn't run, so it doesn't work, you don't get that file. simple?
after this test just remove the line...if the script works, you'll got to figure out some other thing...