Sometimes maximized windows get the window titlebar button in the wrong place. Seen the screenshot in the URL. This has happened to me for a long time. When this happens it also behaves strangely, like th window isn't maximized anymore.
Does this happen even if you change metacity theme? I can't get your screenshot (Can't seem to reach devserv.devel.redhat.com) but I think it's the same I've been experiencing. If it is, it seems to be something with the bluecurve metacity theme that's wrong.
Should be fixed in 2.6.2