I received my new PRS-T1 last week (previously I used a Kindle 3).
I put a couple of epubs from the Gutenberg site onto my PRS-T1. In both cases the book opens OK but I am unable to change the size of the font (Original) and if I select a different font type the book automatically closes, returning me to the home page.
A link to the book http://www.gutenberg.org/ebooks/12234.epub.noimages
I tried an epub from Feedbooks and the font type and size were all OK.