Permalinks mess everything up

I’ve read already many threads on this topic but none of the solutions proposed there seems to be working in my case.

I am just starting to set up a new site with wordpress (www.esperanto-heidelberg.de). At some point I decided to changed the permalinks setting and then my site became “forbidden”. I deleted the .htaccess in the root folder of wordpress (following my provider’s instructions) and the site became available again, but I couldn’t get to any of the individual pages or posts when I clicked on the title.

I also tryed assigning the rights by means of a FTP client, as instructed by my provider, and that wouldn’t do it either. Everytime I try to set the permalinks back to default (it is not really that important to have it the way I want it), a new .htaccess file is generated in the root directory and the page goes back to be “forbidden”.

Can someone please throw some light on this?

Thank you all very much.