When it began? Yesterday, when I decided to switch from WP Minify to W3 Total Cache's Minify Options.
Any more details?
1. The admin bar looks fine on the backend.
2. On the frontend, there's a gap on top of the website where it's supposed to be.
3. I thought that removing WP Minify messed up my theme files, but even with a fresh install of Atahualpa (latest version), the admin bar problem remained.