Just wanted to say that I just got my third Kobo today after sending it back on Tuesday of this week because of the exact problem - blank square in the corner of the screen which actually started growing up the page. My first Kobo had a completely blank screen when it was sent back.
If I did not love my KOBO so much I would not have bothered sending it back the second time. But this will be the last one I do if something happens to it.
