Thank you everyone for your posts.
As further info to some of the questions asked:-
* When I refer to losing my bookmark I am talking about books I was partially through - not something which was just in the list as it had been recently downloaded.
* I have an application called Borders Desktop which is on the PC. I only purchased books from Borders US and used the "update library" function in the Borders desktop app, then Synced to my Kobo.
* After reading through this forum I attempted to use Calibre. The problem still existed. I attempted to add a book which I downloaded through the Adobe software then loaded into Calibre then added to my Kobo from there. Again it took a book I had partially read out of my "I'm Reading" List.
* I can't use Wifi sync - we do not have a wifi connection and here in Australia there are limited public wifi hotspots available ( I don't know why my partner bought a wifi device
)
I am going to try the reset when I get time and see what comes of it.