Permalinks and slugs problem/bug?/feature?

I have strange problem. Recently i updated from 2.3.3 to 2.7.
On my blog i use permalink for posts “/blog/%postname%/”.
My wordpress instalation is with static and post page.
The static page is “/” with slug “home”.
The post page is “/blog” with slug “blog”.
When i go to the /blog page and try to reach the older entries(/blog/page/2/) i am getting error 404. But on /page/2/ i am getting the result.
I have no other permalink problem.
Does anyone know how to fix this?

Please, if you can – help me.