[VMHulme]

I found the cause of the problem! There cannot be any spaces in the merge
field option "text to be inserted before" . When I edit the merge field to
automatically include the text "Ph:space" then merge to a new document -
the merge locks up Word, so I had to delete the space. I didn't even know
there was a space there when I entered it! I had to start from scratch
and merge to a new document every time I made any minor change to the main
document, but eventually I did find that this one little invisible space was
causing Word to stop responding when merging.