custom permalink structure with static text

These issues to help support http://www.anachroblog.com. Thank you!

I would like to use a custom permalink structure:
/blog/%category%/%postname%/
where “blog” is static text.

Category “uncategorized” loads fine at:
/blog/uncategorized/

But post returns 404 Not Found at:
/blog/uncategorized/<postname>/

The only lead I’ve found thus far was here:
http://wordpress.org/support/topic/custom-permalink-error?replies=4