PRS-T1 Sorry - Failure - must close ??

[amyb]

I've been getting a message while reading a book that says Sorry - Failure Error must close (or something similar) and it shuts down my book and returns me to the home screen. When I go back into the book, it's never at the same page and it's changed the text back to the original font. Someone had originally said it could be because of who the book was bought from but it's done it on different books I've gotten from different publishers, so that's not the case. Has anyone else had this problem??