Well, I played around some more, and the error seems to reproduce only
when certain date formats are used in Excel. I've not done an
exhaustive test but under the conditions I posted in my first message:

Word shows "December 2006" if
- system date is set to 2006
- date format in excel is "mmm-yy" or "mmmm-yy" (the excel format
throws this [$-409] bit in front of some of the date formats under the
custom format list, including these two formats, but this seems to be
only a coincidence

I changed the date format in the spreadsheet to m/d/yyyy and Word shows
"December 2005", as it should.

In answer to some of your other questions:
- The connection is being made through the word merge SQL command
SELECT * FROM...
- The field is not derived in Excel; it is entered just as a date

I'd be curious whether or not anyone can reproduce the error given this
information. If not, I'd be happy to upload the word and excel files
somewhere for folks to test.

Frank