I switched from using the "All in One SEO" plugin to the Yoast one on 2 of my blogs that use Atahualpa Version: 3.6.4 and am seeing 2 of the same titles in all pages and posts.

Like this: "Post Name << SITE TITLESITE TITLE"

I don't want to use a newer version Atahualpa. What can I do to fix this?

I posted a possible solution in your other post.

It is best not to double post as it makes for confusion and more work for the moderators.