Humm, that's odd.
I did some researching on Access 2003, Documentor, and the error message you
mentioned, but did not find anything. I did find something concerning Access 2000
so perhaps this article will help in your situation.

ACC2000: Error Message When Running Access Wizards:
http://support.microsoft.com/default.aspx?scid=kb;en-us;303769

Try that and see if that gets the Documentor working.

If you are interested in doing some documentation on your database without
using the Documentor here are some other possibilities for you.

1. I have created a few add-ins that do some specific database documentation.
My "Doug Steele Object Documentor" will create a nice report of all your database
objects for easy reference. The report will list all the objects by category in
alphabetical order in a three-column layout. It looks very sweet in my opinion
and it's even easier to use than the Access Documentor. Plus, you get a nice
report saved in your database that you can open again any time you wish!
There is one version for Access 97 and another version that works for
2000, 2002, and 2003.

You can find the free Add-In on MVP Doug Steele's site here:

http://www.accessmvp.com/djste?ele/Documentor.html

I also created an Access Add-In called the "John Viescas Table Documentor"
that documents the table structures. It is even easier to use than the built-in Access
Documentor and creates a slick report that will list each table (including
linked ones) and their field properties in an easy-to-read format. I recently
finished Version 2.0 of the add-in. This version even works on MDE files.

This add-in has not been posted yet to a web site so if you would like
a copy please let me know.

I have another add-in called the "Albert Kallal Database Statistics"
that will make a one-page report that lists the total number of lines of code
in Modules, Forms, and Reports (a sub total for each and a grand total)
as well as a count of each other type of database object (a sub total for
each category and a grand total).

This add-in has not been posted yet to a web site as well so if you would like
a copy please let me know.

I have another add-in that will, among other things, document the User
and Group permissions in a secured database. You can find that add-in
on MVP Sandra Daigle's site here (at the top):

http://www.daiglenet.com/msaccess.htm

2. David Hare-Scott has also written a simple table documentor.
You can download it here:
http://www.rogersaccesslibrary?.com/OtherLibraries.asp#Hare-S?cott,David

3. Armen Stein has something here as well:
http://www.jstreettech.com/cartgenie/pg_developerDownloads.asp
(Look for Data Dictionary Report Utility)

4. You can buy a commercial product like this one that will produce a wealth
of information:
http://www.fmsinc.com/Products?/analyzer/index.html

Hope that gives you some ideas.
Let us know how it goes.