I just installed Ubuntu 12.04 LTS 64 bit on a machine, everything went well accordingly but after login it just gives me a blank screen. During startup after BIOS message it shows "Out of range" error and comes to login window after logon it's just a blank screen. even after somehow it comes to an empty desktop screen i dont see the Unity bar or anything like that (Can change wallpaper, and system setting though). And can't goto Console mode by pressing Ctrl+Alt+F1 - it returns "Out of range" error. System is new AMD Sempron with 2 Gigs of RAM has NVIDIA GeForce 6150SE-based graphic chipset. any ideas on this?