I followed the instructions in the link you supplied, and while it worked as
far as removing the introductory dialogue box, it didnt resolve my original
problem. Even with the changes in place, I'm still having issues getting Word
to merge in certain circumstances.

Here's a little additional information:
We're attempting to print form letters, filtering by letter date and letter
type. This throws up an error. If I filter the same information by letter
type and then letter date, it seems to work just fine. The only difference I
can tell between the two methods is that when sorting by date, you have to go
into the advanced filter panel and type in the date, whereas the other method
is accomplished through only drop-down menus.

Thanks again