@NiLuJe: Your screen-shot shows the same error. At the bottom of the right column you see somthing that looks like
_____|_____
Originally this looks like
prev | next
The prev/next buttons are still working the way the schould - even if the text is unvisible.
A few weeks ago I installed Jailbreak (0.7.N), Fonts (4.7.N) and Screensaver (0.23.N). In installed the linkfonts directory but didn't replace any font in linkfonts/fonts. At that time the prev/next text were still visible.
A few days ago I installed three newer versions of the Hacks mentioned above. I also removed the linkfonts subdir from Version 0.23.N and replaced it with the linkfonts subdir of version 0.24.N. The prev/next text became unvisible.
I tried to replace fonts in linkfonts/fonts with Diavolo_K3, FertigoPro_K3 and Fontin_K3. The next/prev text didn't come back. Currently Fontin_K3 is installed on my Kindle having a smaller font within the Sections&Articles menu then the original Kindle fonts.
Please see an example at
http://www.kindleman.com/help/format/ The prev/next buttons also appear at the bottom of the left (Sections-)column if the number of itmes doesn't fit on a single page.