upgrade 2.6.3 blog wont display – admin section ok

After upgrading to the german 2.6.3 version, the admin section works fine, but the blog doesn’t display – instead I get an error message:
Too many redirects occurred trying to open “http://XXXXXX”. This might occur if you open a page that is redirected to open another page which then is redirected to open the original page.

Any suggestions what I may have done wrong?