So, finally, FINALLY, I figured out what the problem was (and yes, I am proud to say that I figured it out all on my own!).
Word2008 and EndnoteX3 were both properly installed on my PowerPC Mac, both working away happily, but unwilling to talk to each other. Our IT guy upgraded my OS to Leopard (apparently there isn't good support for Snow Leopard with Power PCs, like there is for Intels). And....drumroll... nothing.
After following all of the instructions in Endnote's pdf, all three techniques, to no avail, I had a wild idea. Perhaps the Word Startup file (even though I explicitly defined it) was not programmed smartly enough to look where I told it and, because of being on the afs server (So now my "home" directory isn't under "Users), it couldn't find the template files that allowed it to communicate with Endnote.
So, what I did was moved the template files to the Word Startup directory on my local machine (instead of the afs server), and - ta-da!! - it works! Yay!!!
Yes, yes, I am a technological genius.
But, as punishment for it taking me so long to figure it out, I now have a new operating system, and all of my applications have been erased (which our very nice IT guy neglected to mention). F. I know it shouldn't make me want to cry, but it does. I could have at least made a list of everything that was going to get erased. Guess I have something to keep me busy the rest of the day, and tomorrow - figuring out which programs are missing and which versions to install. F.