I recently installed Ubuntu 12.04 onto a new computer I built and everything ran great, so I installed Openjava 6 & 7, downloaded the minecraft.jar, made sure it ran as an executable, and logged in. It downloaded the game and went to what is normally the Mojang screen. Once it tried to load the main menu, it refreshed my screen, and when it came back, the sidebar and topbar were both gone, and only the desktop and background remained. I rebooted, and even the log in screen is like this. Any help?