Thanks to photographer and writer, John Beardsworth, for his help in sorting out keyword back-up. See yesterdays Post.
Check which version of Bridge you're using here. The Adobe Bridge Keywords.abdata file was only used up to version 1.01 of Bridge. The version 1.0.2 update (which Adobe strongly recommends) changed this to an .xml file called Adobe Bridge Keywords.xml. It left the redundant abdata file in place.
He also informed me that the new back-up file type can be found in the same directory as the .abdata file. I updated to 1.02 yesterday. You should too.