The first thing I would do is make sure your directory is a Trusted Location in both MS Word and in Access.

File -> Options ->  Trust Center     then Click Trust Center Settings

Then depending on how your network is set up RIGHT click on the Shared folder in Explorer and Chose the Security Tab.  You may need to change your security setting for that folder.

Thanks for the ideas, Scott. Alas, it didn't work.

I made the folder a trusted location for both Word and Access. In the security settings, that folder shows "everyone" on the network as well as the user and admin logins for this computer are all set to allow:
full control
modify
Read & execute
list folder contents
read
write

But I'm still getting that same error. Access locks up after I close Word and all the error messages. I have to force quit.
I tried using a different Word file, but same problem.

I tried moving the Word document to the desktop - same error. I tried moving both the database and the Word file to the desktop - same error, but it references being unable to find the desktop instead of the folder.

So the problem is maybe Word trying to find where the Access file is. Depending on how I click out of all the error messages, I get a new error that says Word can't find the file.

We have Office 365 and have often done Word-Excel mail merges.

Hm. I tried opening the Word document first and working through the mail merge wizard there. It does give me the option to choose Access as a data source. However, the list of tables and queries to select from is incomplete. Several queries are missing, including the one I need to be able to run this merge.

Try creating a .udl file and see if you can connect to the database that way.

Alex that one is new to me even.   I've not heard of that file type.
Would that be in Access or Word?

Just on the desktop, name it anything, with that ext, then double click it, and fill it in,

Katherine -
I don't know why you aren't seeing your queries - unless they are too complex.  

Could you try a real basic merge using Richards Blank Template and see if Word will connect to that?  Say using the customer table.

Net trouble shooting I would try is merge directly from a table.  No queries no criteria.  Does that work?

If that works - could you copy your query that you want to use for your merge and make it into a make table query creating a temporary table.
Try using that for your merge.
Your queries (in the past) have had so much going on- making calculations etc. It might be that making the TmpTable is the better solution any way.  I have an idea it may make the merge less prone to problems.  You are just taking a snapshot of the data as of the time of printing any way.

OK, it's confirmed - my problem is the query I'm trying to use.

I did the .udl trick, but I first tried it with just my HouseholdT, and it worked no problem.

When I tried it with my MemberMailingQ, it failed to work, even if I deleted the criteria in the query.

It's interesting to me that it's not necessarily queries that have user-entered criteria that don't work, or queries that are non-modifiable. But for whatever reason, some queries are just not OK for mail merges. Doing a mail merge the reverse way from Word will give the list of what works and what doesn't.

So I'll need to resort to a maketable query, or just set up a button to export the query as an Excel file.

Thanks for helping me troubleshoot this!