Problems with permalinks, next_posts_link

Hi,

my new theme is nearly finished. But one big bug I didn’t get fixed:

– I have a static start page
– all blog-post are under “blog” (http://www.etes.de/blog/)

Now: If I want to list older posts (next_posts_link) on this side (here in german ‘ältere Beiträge’) I get an 404-page. Until now the link is ‘etes.de/blog/page/2/’

If I type in the url without ‘blog’ (etes.de/page/2/) I get the older posts. But that is the wrong permalink.

If I’m in on a single post, the navigation works!

I set the permalink-structur to manual: /blog/%postname%/

So what ist wrong? An error in the database?

Thank you for any idea!!

Greetz
Achim