Problem with updating authors names in endnote library

Im using word 2008 for mac version 12.2.5 and endnote X3  Ive just started having a problem in trying to update fields on my large endnote library  such as authors, it will take a full 100 seconds to do this. 

I have recently saved  my endnote library to an ext hard drive, but am working with the original on my laptop. 

My endnote library is large, 1200 refs most with notes and files attached.

How do i  get this back to being user friendly again?