I18N language in URL index page problem

[ChriS]

Is someone using GS 3.0 and I18N 2.5.1 Navigation with "Include Language in URL"?
While without "%language%/%parent%/%slug%" permalink setting and edited .htaccess everything works fine, afterwards I have problems with the index pages. Every other page (Parents and Subpages) is working, for example "/de/vacations/". But not the link to the index pages:
/de/
/it/
/en/
Everyone gives a "Oops! Page not found!" with I18N edited Innovation Theme.
The link to the root "/" shows the index page of the Page Management Setting "Language of all pages with URLs without language code (like "index"), e.g. "de": ". In my case this is "de".
Here the .htaccess-code

Code:

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(de|it|en)/(.*?/)?([A-Za-z0-9_-]+)/?$ index.php?id=$3&lang=$1 [QSA,L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule /?([A-Za-z0-9_-]+)/?$ index.php?id=$1 [QSA,L]

Even with using copy and paste from mvlcek.bplaced.net/get-simple/i18n there was no change in the behaviour.
After some hours of testing (on local WAMP-Server) I ask me if someone can reproduce this or do I have a nasty bug in my code?