Sorry about the false start.
I've just tried reproducing your problem on 8.04.2 with nautilus 18.104.22.168 and nautilus-actions 1.4.1-1ubuntu1.
I don't think the script itself or what is passed on the command line are significant -- I configured nautilus-actions with a non-existent script and the entry still showed in the context menu for an empty file called a.flv
Have you tried restarting nautilus? It wasn't necessary when I tried reproducing your problem but it did solve a couple of problems of nautilus-actions configurations not taking effect in my initial usage.