Success! I installed 0.7.5, checked that I have teh new box ticked and 'tags' set in sony device plugin -imported converted and tagged a pdf book. Hooked up my 505, sent the book over - and my book was sent to the 505 *and* all the 258 books on there (which lost their collections earlier) are now back in their collections
I *know* the recommendation is to delete and resend teh books, but since I'm going to keep running Calibre in debug mode, I decided not to do that, and instead see what - if anything - turns up later
Thank you for the quick fix to the collectons&tags issue