I just discovered an undocumented config-parameter to deactivate SEO URLs:
So if you want to switch off SEO-URLs, just put the following line on the bottom of your config.inc.php file:
Thanks for this tip, i was just going mad with the given .htaccess-Solution. Now it works, except the Tag-Cloud shown on the Home-Page seems to be buggy. Everything else works flawless as far as i have seen till now.
But maybe, someone will find a solution, not only a workaround for this given SEO-URL-not-.htaccess-compatibility