Bookmarks become inaccessible - I click the bookmark folder and it doesn't dropdown. When I first open Firefox I can click on any bookmark folders on the Bookmarks Toolbar and the folder drops down presenting my bookmarks. I can also press Alt to reveal the Bookmarks menu, and anything on this menu is accessible. After a while (haven't worked out how long, or after doing what particular thing), when I click a bookmark folder, whether on the Toolbar or on the Bookmarks menu, nothing works. When I click, the folder goes darker, a line appears under the folder name, but the folder doesn't dropdown. It's almost as if it's dropping down behind the main window, but is totally inaccessible. If I try pressing Alt, I get the menus at the top, but clicking on Bookmarks doesn't do anything, and nothing else on the top menu works. Clicking an individual bookmark on the Bookmarks toolbar does work. At this point, the Firefox menu (the three stipes button) doesn't work either, nor anything else along that toolbar, apart from the Home button. Restarting Firefox resolves the problem ... for a while. Has anybody else experienced this?