FWIW I can easily replicate this problem here with some simple test data.
What to do about it is a different question...

Word will certainly eventually see new records that conform to any filter
you have defined. e. g.
a. in Word, I select all records in table t where f='paper'
b. in Access, I add a record and set f to 'paper'
c. in Word, I use the arrow keys in the mail merge toolbar to navigate to
the last record
d. the new record appears.
e. in the new record, I change 'paper' to 'scissors'
f. in Word, I navigate away from the record that now contains scissors,
then back again. Word still sees the record despite the fact that it now
displays field f as 'scissors'
g. FWIW if you open the Mail Merge Recipients dialog box you also see this
record. If you click Refresh, it disappears.

I do not know whether this behaviour is a direct result of the way the OLEDB
provider works, or a result of the way that Word configures or uses the
provider, or what. It is possible to change some of the properties Word uses
when it connects to a Jet database by specifying properties in a .odc (or
maybe .udl) file, but (for example) changing the open mode to Read doesn't
do the trick - I suspect the only thing that might would be to change the
type of cursor used, and I do not know if it is possible to specify that in
a connection string: I don't think so.

However, what does seem to work, at least in the simple test scenario I have
here, is to use an ODBC connection instead of an OLEDB one (check Word
Tools|Options|General|"Confirm conversions at open", go through the
connection process again, and select the ODBC option when it is offered).
However,
a. Word won't see Unicode format data via an ODBC connection
b. the data in some field types (e.g. date time and yesno fields) is
returned in a different format when you use ODBC.

Wish it was simpler...

Peter Jamieson