My xubuntu 12.04 has worked flawlessly since install in September. However, lately I randomly have the following boot issue : The computer boots to grub, and after choosing xubuntu either boots normally or boots to a black screen. Here are some observations I have made : The black screen seems to happen randomly. The black screen does not seem to happen in safe mode (- nomodeset in grub). The black screen does not allow me to ctrl + alt + F1-6 into a terminal. The black screen allows me to use SysRq keys (Alt + SysRq + K does not work though). The black screen often happens on first boot in several hours and the computer usually boots normally after a RSEINUB. When the computer boots I get "SP5100 TCO timer: mmio address 0xfec000f0 already in use" at startup and "Could not write bytes: broken pipe" at shutdown. However research on these errors did not yield answers to my particular issue. Comparing Xorg.0.log (successful boot) and Xorg.0.log.old (black screen), and reading the answers to similar problem, it seems that I might have a X driver issue. However the system worked flawlessly since lately. Additional info on my system : ACER AO722 C62kk Operating system : 3.2.0-31-generic ubuntu Edit : I made a fresh install of Xubuntu 12.04 x64, the issue is still there ... (I have a separate /home so config. files were not erased). Edit 2 : I followed troubleshooting blank screen, so my new observations are without quiet and splash in grub : When the system boots normally, the screen goes black after grub then lights up and displays text information then goes to login screen. (After that the desktop starting time vary substantially, which is new and may be a separate issue ?). When the boot fails, after grub the screen goes black, lights up, goes black, lights up again and most times goes black again. At this point it responds to Alt+SysReq K by lighting up but no more, and has to be rebooted through Alt+SysReq+ RSEINUB. Thank you for your time and attention in advance ! Thibaud Ruelle