Re : Changings in language.php
Hi Bjorn,
English has a special status in Tiki, it is used as a "root language". This means that strings are written in the code as "english string{/tr}" which calls a function to use language.php to translate "english string". If the translation is not found, the english string is shown.
The directories you're talking about were not created on Tiki installation, but when Tiki created its cache. Consequently its Apache that owns them. You'll have to su to chown them, although if Apache owns them there shouldn't be problems at first glance.
Good luck anyway, try to visit IRC #tikiwiki and you might find help there.