The on the WMF servers currently used GeSHI Version have some highlighting issues that are fixed in the current version (see http://qbnz.com/highlighter/)
The image GeSHi_2.PNG was made on wikibooks, GeSHi_3.PNG on http://qbnz.com/highlighter/
Failures are for example "typename" in the first row and const in the last row.
As written on http://www.mediawiki.org/wiki/Extension:SyntaxHighlight_GeSHi it's not caused by the extension, it's simply an old revision of geshi it self. To fix that, please repeat step 2.
The update will also add new languages and change some colors, see also http://qbnz.com/highlighter/news.php
(I don't know which version we allready have, special:version doesn't show it)