If the "Menu Bar" is hidden then the Menu bar gets replaced by the orange Firefox button. In Firefox 3.6 and later on Windows you can hide the menu bar via "View > Toolbars" or via the right click context menu on a toolbar.

Press F10 or press and hold the Alt key down to bring up the menu bar temporarily.

Go to "View > Toolbars" or right-click the menu bar or press Alt+V T to select which toolbars to show or hide (click on an entry to toggle the state).

See also Restore the Menu bar in Firefox and http://kb.mozillazine.org/Toolbar_customization

Also, and although possibly not related to your problem, I have to remind you that the version of Firefox you are using at the moment has been discontinued and is no longer supported. On top of this, it has known unpatched bugs and security problems. I urge you to update to the latest version of Firefox, for maximum security, stability, performance and usability. You can get it for free, as always, at getfirefox.com.

I had the same problem, and here's how I resolved it.

Click on View > Toolbars > Customize, drag the bookmark icon to the toolbar. Click on the bookmark icon you've just dragged to the toolbar. Click the plus sign next to "Bookmarks Menu" to bring up your bookmark list.

Hope this helps the rest of you with the same problem. (I'm using FireFox 3.6.12.