I moved one of my blogs onto my main site, so, now there are 2 blogs there, side by side.
Trouble is, when I click on an article in Blog A, it suddenly switches to the theme of Blog B, and says "page not found". See:
To do the move, aside from moving the blog files themselves, I updated the following mySQL settings:
wp_options >> siteurl (I put the new URL here)
wp_options >> home (same)