Not sure, but it sounds as if something thinks you have some "e-postage"
application installed but does not find the necessary components when you
try to merge.

Suggestions:
a. have a look in Word Tools|Templates and Addins for anything that looks
as if it may be an e-postage addin that should not be there. If you find
one, you can disable it temporarily by unchecking the box next to its name
in the list and see if that makes a difference, but you will probably need
to select it and use the Remove button to eliminate it altogether.
b. if you are initiating your merge from the Mail merge Wizard, try using
the toolbar instead (Tools|Customize to enable it, and the various buttons
for doing the actual merge are near the right hand end).

Otherwise, it may be necessary to have a look for e-postage entries in the
registry. Or something else altogether.

Peter Jamieson