First question: were these columns created in the individual libraries,
or did you create site columns which you then added to content  types which
you then added to each library... or is this some in-between combination?
If I had to guess, I'd say that the first option is what you have happening
here. As a result, these columns are not identical, so SharePoint will try
to fit them all in.
Regarding your naming question, the fields may have the same *display
name*, but I'll bet if you go into the Library Settings and try to edit a
column, you'll find that the name of the column in the URL is not the same
as its display name. This is how these guys stay unique.
Though I haven't tried this myself, I would venture to say that if
you're going to have identical content types in different libraries, then
you'll want to create site content types at the highest level possible and
use them in each library to ensure consistency in the future.

Does that help at all?

Your first guess is correct. These were actually old
lists from our SPS 2003 site, and I was trying to clean up and
consolidate some stuff. None of these use "site columns" or "content
types." I will go and check to see what you mean about the URL name.
It's probably a guid, right? Yeah, I wish they'd provide "display
name" and "url" separately for columns the way they do for views.
It'd be easier to update them, for sure!

I will certainly be exploring all of the advantages of site columns
and content  types in the near future. There is still so much this SPS
girl has to learn about MOSS... :)

Thanks for your help! Microsoft should definitely explain this
better before encouraging folks to move items  around via this new
tool. I can't imagine I'm alone w/ this problem. What a mess.

No problem; this stuff is still not very well documented, as you know

One thing about what you said below: the actual field names -- as opposed
to the display names -- are not actually GUIDs. You should be able to see a
field name in the URL (I don't remember the parameter name and my SP VMs
aren't spun up right now) that may look similar to the display name, i.e.
it should be something you can recognize.

You are correct- the URL displays the guid for the list, and then
says "field=____" and the column name. It simply puts a 0,1,2 etc.
after the field name if the (display) names are the same. I was able
to quickly double-check to make sure nothing was in the columns w/
the numbers in the name, then I deleted them. In all cases but one,
they were empty. I'm still a little confused as to how they were
populated in one of those "new" columns- it was in a doc library, and
the original and one of the new columns w/ the same name both
actually had metadata for two documents. I'm not too concerned w/ it,
but I did find it odd.

I cleaned up everything, and I feel like I've learned a lot today.
Thanks SOO much for your help!