That’s with the Twenty Eleven theme, right?
If so, the issue is known and will be fixed in the next release. Here is a workaround for now:
1. Install and activate the plugin Custom CSS from https://www.ads-software.com/extend/plugins/safecss/
2. Add the following on the new Appearance > Edit CSS and replace the full content of the stylesheet editor field with
#branding {
z-index:999;
}
and hit Save Stylesheet. It will appear as if it was not saved (it’s a bug) but refreshing the admin page should show that the content of that field is now like above.
Check your sites front-end again.