FF3usME v.6.5 Error

I'm not sure why it's doing that. Try expanding the ROM if you have not already. I remember getting that Error with the Mag Roader Script, when using a fresh ROM. But after saving it did disappear. And while this doesn't have anything to do with it, A newer version of ME is out, found on Lord J's website here: http://www.angelfire.com/pq/jumparound/d..._Beta2.zip

The only other suggestion I have is to try a different ROM's. One with a header, one without, version 1.0, version 1.1. And just make sure after you make a change in the script, you press "OK", and then "SAVE."
do very small tests to make sure it is working first before you put in a bunch of work. For instance try changing the Narsh Guards attack to Ultima, then press OK and SAVE, then test it out. It SHOULD work, there is no reason for it not to be saving.