Maybe.

Which version of Word is this? 2002 or 2003?

By this, do you mean that it appears somewhere in your document as a list?
If so, use Alt-F9 to reveal the field codes (with curly braces {} arounf
them) in your document and see if you have any DATABASE fields in your
document. I'm not sure how one could have crept in accidentally but there
you go.

How did you create the original list?
- If you created it using the "Type a new list" option in the Mail Merge
Wizard, Word creates a list called an "Office Address List" with a .mdb
(Access/Jet) extension. You /should/ be able to use the Edit button in the
Recipients dialog, unless you have
altered the structure of that .mdb, e.g. by editing it directly in Access.
- If you created it yourself in Access, then typically you are not allowed
to edit the list at all from the Recipients dialog box - you have to open
Access and edit the data there.

If you do have Access, I would consider trying the following
a. close Word and Access, and make a backup copy of your .mdb (just copy
the file in Windows Explorer
b. try editing the file in Access
c. re-open your Word mail merge main document and see if the changes are
reflected in the preview or merge output.
--
Peter Jamieson - Word MVP
Word MVP web site http://word.mvps.org/