Touch Unreadable EPUBS after upgrading

I have upgraded to 2.3.1, logged out and logged back into my account and reinstalled ADE and sync'ed.

Now all my old Gutenberg and other EPUBS on my Touch are unreadable - they just show blank pages. The Kobo Welcome Guide is also unreadable - it may have been decreased in size to about 1cm square, there is something on each page but I cant see what it is. The paid for Kobo books work fine.

Any help much appreciated.