Like Christian said, it seems like you have a problem in the graphics configuration.
What graphics card are you using? Did you install proprietary drivers, or are you using the standard drivers? Did you update the drivers at all?
To find the details of your driver, run
lshw -class video, and look for the line with "configuration". The loaded driver is prefixed with "driver:".
~$ > sudo lshw -class video
description: VGA compatible controller
product: GT216 [Quadro FX 880M]
vendor: NVIDIA Corporation
physical id: 0
bus info: pci@0000:01:00.0
width: 64 bits
capabilities: pm msi pciexpress vga_controller bus_master cap_list rom
configuration: driver=nvidia latency=0
resources: irq:16 memory:cc000000-ccffffff memory:d0000000-dfffffff memory:ce000000-cfffffff ioport:2000(size=128) memory:cd000000-cd07ffff
In my case, since I am using the NVidia prop. drivers, I can check the driver version by running
dpkg -l | grep nvidia which returns:
~# > dpkg -l | grep nvidia
ii nvidia-common 1:0.2.44 Find obsolete NVIDIA drivers
ii nvidia-current 295.40-0ubuntu1 NVIDIA binary Xorg driver, kernel module and VDPAU library
ii nvidia-settings 295.33-0ubuntu1 Tool of configuring the NVIDIA graphics driver
There could also be something wrong with the X Server configuration in the file
xorg.conf. Open up that file in a text editor, and paste the contents here.
~$ > sudo -s /* enter root */
~# > find / -name 'xorg.conf' /* find file, search in all directories */
~# > exit /* exit root */
~$ > gedit /etc/X11/xorg.conf /* open file in editor */
Depending on how that file looks, you can reset the xorg.conf file using the terminal by doing
sudo dpkg-reconfigure -phigh xserver-xorg which will automatically generate an xorg.conf file while backing up the current one.
You can also delete the xorg.conf file. Then restart the X session with
startx. Doing so will create a brand new xorg.conf file with the absence of not having one.
Hope that helps.