[Plugin: WordPress SEO by Yoast] New update adds blog title at top of the page

The answer to your question can be found here:

http://thematictheme.com/forums/topic/wp-seo-make-double-site-title-and-description/

Maybe I should create different topic, but same for content on single post/page with WordPress SEO + Thematic (childtheme)

[update]
to clear problem, plugin (1.2.2) with Thematic 1.0.1 created double content block.

here is screenshot http://mediabox.lv/20120619_1340135802757.png (ignore displaced wordpress adminbar 🙂 )

same with WordPress SEO 1.2.3 😐

Source code: http://mediabox.lv/thematicwpseo.txt

WordPress 3.4
WordPress SEO 1.2.2, 1.2.3
Thematic 1.0.1

No problems with:
WordPress SEO 1.1.9
Thematic 0.9.7.7