If the progress bar stalls at the very end, i believe it means u are missing a Desktop Environment such as gnome/kde/xfce/lxde/etc or the DE is not configured to startup correctly . I always boot up by holding the home key as soon as i select ubuntu form the boot menu to reach the recovery menu and then choose activate console on frame buffer to be able to monitor the loading progress as well as be presented with a shell login when it is done. I dont use gdm so i login through the console and then just startx ( i have gdm-core installed instead of ubuntu-desktop)

Hope this helps some1