Every sidebar, including the ones 'bundled' with Firefox i.e. bookmarks and history now opens above a browser pane. If you like as two windows but to be correct panes. These 'tools' work, but now take up a large amount of space. I have also noticed that the new 'progress bar' now sits at the top of the browser and covers my bookmarks etc tool bar. The Adobe Acrobat update installed the Chrome browser a couple of days ago, so I am wondering if this has altered any settings.