Navigation-Bar stays empty - No Pages / No Postings

Hi folks,

after using the RC1 for couple of days, today i upgraded to wp3.0-Release.
Everything went fine! All my blogs are still there and alive.

On a new (sub)-blog i tried the Product-Theme. Fantastic!
But: the Navigation-Bar stays empty. No Pages or Postings are showing up.

May you have a look:
http://livingbooks.rk-newmedia.com/
One example page (there are more):
http://livingbooks.rk-newmedia.com/schoenheit-des-alters/leseprobe/

PS: buddypress is not installed. Hope, thats no problem.

What can i do. Any hints...?

Many thanks in advance,
Rainer.