Posts won't open unless I select them using Categories

I have the main blog and several sub-blogs, all with posts done from Admin.

First, I cannot find a reliable way to post into a sub-blog. I go to Dashboard, MyBlogs and set Primary Blog to the sub-blog path I want to post to. Sometimes this works but most of the time my post still ends up in the main blog.

Second, even after getting posts correct, I cannot view the posts in the normal fashion.

1. If I select the Category I assigned to a post, I get a list of the posts. Selecting a post opens the post properly.

2a. If I select Blogs, I get a list of the main blog plus the sub-blogs. Doing "Visit Blog" for the main blog takes me to a blank page with no way to display the posts.

2b. Doing "Visit Blog" for a sub-blog takes me to a page saying "Sorry, we can't find the content you're looking for at this URL. Please try selecting a menu item from above or to the side of this message to get where you'd like to go."

How do I get posts to blogs to work properly?