I have the Bookmarks selected to be displayed on the left Side Bar. I open Firefox and the Side bar displays my bookmarks OK. I like to use two or three windows (Instances) of Firefox. Occassionally, when I open the 2nd or 3rd Window, the side bar on the 2nd or 3rd Window is blank and Bookmarks no longer visible. The only way I can get the Bookmarks to display on the 2nd/3rd Windows is by going to the main menu on top, select View / Sidebar/Bookmarks. I have had this issue for couple of years now on different versions of Firefox and the same issue exists on Windows 7 as well as Mac OSX platforms. Currently running Firefox v31 on both platforms and have current Windows 7 updates as well as current MAC OSX Maverick updates. I am running Microsoft free antivirus on the PC and no virus app on the Mac. Your help in solving this issue is greatly appreciated.