I found under Ubuntu 11.04, there is a nerfarious Compiz Bug. You click on the “menu” button on the window, and the drag bar disappears from all your windows. You can rectify this temporarily by opening a Terminal and typing:
Fix. Go down from “Applications” on the menu bar to “System Tools” and choose “Compiz fusion icon”. The icon will appear in the menu bar on the right. Right click and hold down the mouse button, and choose “Select Window Manager”. Change this from “Compiz” to “Metacity”.