Created attachment 459896 [details] screenshot: titlebar two ways! On my laptop, in which I *believe* I have selected Aero without transparency, I get the behaviour from the screenshot: we draw the Minefield button in the titlebar area, and the tabs overlap it, but we also overdraw with the old-school titlebar too. Intel graphics, d2d disabled. let me know if you want me to dig around in the windows settings to get more information for you.
The investigation of what's going on here at least blocks a beta.
Is this constant? or something that shows up once in a while? Might be a dupe of bug 545892.
Yeah, I noticed it happening with Foxit as a full-page plugin. Could well be a dup, I'll reopen if I see it without plugins in play.