Running a blog can create alot of duplicate content issues since these systems sometimes create multiple versions or other problems. One example of a Wordpress issue is that they provide the option of publishing your pages using keyword rich urls instead of the old numeric urls. This caused problems in the past since it also would create both keyword rich urls and numeric urls thus duplicate content. In general it wasn't a big issue since the numeric pages normally didnt have any link popularity, but it was not a good thing.

[wordpress.org...] is a good resource for handling Wordpress issues. Since so many people use Wordpress it is likely you are encountering an old problem that they already solved on that site.

If you want to block the bumba category here is how you would do it.

User-agent: *
Disallow: /archiblog/mumba/bumba/