This is from a response by Peter Jamieson to another post that probably
explains and suggests a solution (DDE) to your problem:

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Your best short-term bet, assuming you have Excel on your system, do not
have non-ANSI Unicode characters in your Excel sheet, and have the data in
the first sheet of your workbook (and probably other stuff as well...), is
to try changing the way Word gets your data to the old method (DDE): check
Word Tools|Options|general|"Confirm conversion at Open", go through the
connection process again, and select the DDE method in the additional dialog
box.

Assuming you are using Word 2002/2003, the problem is that the OLEDB
provider that Word uses to get data from Excel tries to determine a data
type for each column. It looks in the first 8 or 25 rows and uses the data
type it finds for the rest of the column. When the types are mixed, it takes
the "majority type". The trouble is that it regards text less than 256
characters long as "text" type and longer ones as "memo" type, and there are
also additional special rules when dealing with texts and memos. You /might/
find, for example, that by adding enough trailing space to shorter texts in
the same column, the whole thing springs to life again.

I'd point you to the web pages I'm writing on this but there are so many ifs
and buts that it's taking me forever to complete.

Peter Jamieson

Unquote