So I noticed the problem with quite a few ebook files and I was about to call Sony to request authorization to send back what I thought must be a defective unit. Consulting the manual I found resetting the reader as a suggestion for many problems. So I tried that and it seems to have done the trick for now.

There is an annoying problem that remains though. Links within the text do not seem to work. I am speaking of, for example, ebooks from this site where superscript numbers for footnote citations in the text are hyperlinks to a page of footnotes. Pressing the superscript numbers does not seem to do anything. Anyone else noticed this for the 900? If it is a problem it will effect how I put together the epub file I am working on now.