Internal server error Using Joomla

Hello, I'm setting up a joomla website using nginx 1.2.1-2.2 on Raspbian wheezy. The homepage is displayed properly. But if I add another site (called "collection") and click on the menue button I got a 500 internal server error.

Error log says:
2014/12/16 17:20:42 [error] 14546#0: *45 rewrite or internal redirection cycle while internally redirecting to "/index.html", client: xxxx, server: smtagore.de, request: "GET /index.php/collection HTTP/1.1", host:"xxxx:8001", referrer: "http://xxxx:8001/index.php"

I've checked relvant posts since hours but can't fix it.

Any idea where to start?

I gladly give more information, whatever is needed.

Best,
AndRi22