User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:7.0) Gecko/20100101 Firefox/7.0 Build ID: 20110816154714 Steps to reproduce: After installing FF7 beta, the icons in the navigation toolbar seemed unusually big, most noticably the "back" button, which should be round in appearance, seemed streched to be oval or egg shaped. Notice: the actual "icon" does not change it's size, merely the "container"/frame/border gets bigger. (See picture attached with both the normal sized version [top] and the unusually big sized version [bottom].) Actual results: While customising the toolbar, I set the icon size to "small" ("use small icons") and then back to normal/big sized icons. The icons regained their usual look, ordinarily big and (in case of the "back" button) round. After closing firefox and restarting, the icons where oversized again and could only be transformed back by setting their size to "small" and back to "normal" in the customize window. Additionally opening a new browser window will result in opening a new window with oversized looking icons. Expected results: The icons should keep their normal size and not get bigger by themselves. ;)

The issue seems to have a connection to specific (add-on) icons in the toolbar. Certain combinations of "Adblock Plus" and "Download Helper" (from http://www.downloadhelper.net/ ) seem to cause the problem. Removing both icons eliminates the bug, but I seem to be unable to find out exactly how to trigger it.