yeah, I think they are being converted to kepub.
The kobo utilities lets you send cover images to the N905 seperate to the epub. That just wasn't working at all.
The default image is just a blank book cover image, so you can see something is there in the gallery view. With 1200 books, thats a bit of an issue to browse.
This is happening with store bought stuff with covers in the file, not just ones I've converted from PDF or txt. It's just the epubs when they are converted.
I know its bizzarre, but reverting back a few versions has fixed the issue.
I'll see if i can get the time to post the logs over the weekend. Having a second kobo should make this a lot easier to do
Seeing as tech support is my day job, it should hopefully make a bit more sense than 2am rambling.