Reported by Atethnekos on EnWiki, who also provided an image: https://en.wikipedia.org/wiki/File:Platovesample1.png
"When I edit a page with the pending changes revision dropdown, and I am scrolled to the very top, the dropdown and the VE page settings link become mangled. See highlight in included image. Firefox 22 on Win7 Pro SP1."
I can reproduce this in both Firefox 22 and Chrome 28. The issue seems specific to the Monobook skin - Vector renders the pending changes dropdown somewhat lower in both browsers.