Wow, in my case, it actually shrunk to 75% and moved to the middle of the
slide. I'm sure this is because I typed enough text that it dropped to a
second line in some of the cells in Word.
I think it's got to do with the text fitting in the cells -- PPT tries to
still show the whole thing on one row, and in order to be able to do this,
it either shrinks or enlarges as (it thinks) appropriate. Actually, I always
struggled with Word 2003 tables resizing in a similar manner in PPT 2003, so
it may just be an old OLE issue that's still cropping up. (When you insert
objects like this, you're creating what are known as OLE -- object linking
and embedding -- objects.)
I'm not sure if this is a bug or "by design," but regardless, it sure is
annoying. You can right-click and choose Format Object and resize to 100%
size on the size tab. I know that's not ideal, but it's the only thing I can
think of right now.