I used /index.php/%year%/%monthnum%/%day%/%postname%/ before I updated to 2.0. Having the brand new thing up and running I chanced on of the other permalink options. The result was a 403 on admin-panel and frontend. Only way to get back in is to upload a new empty .htaccess but the the permalinks are still set to the new option (%year%/%monthnum%/%day%/%postname%/). Any klick on a headline still leads to a 403.
Any idea what the f*** is going on and how to stop that?