Sorry for pulling up an older thread-- but I'm a new Kobo Mini owner, having some related issues. In my case, it involves epubs from my public library downloaded via ADE. 2 of 3 lack the option to adjust font size. This is not an issue with purchased titles from Kobo.
Upgraded ADE, did full reset, but the problem remains. Not having functional library titles is a big drawback-- though my Nook ST will be glad get my attention again.
Any ideas? TIA.