Don't run apt-get upgrade yet. It'll just download and install 500MB worth of software and the problem will come back on next reboot. Also keep in mind that updates have to be installed on hard disk installation. Don't run this command on live DVD boot Now you have to download and install drivers for your graphics card. Mine is a NVidia and I downloaded my drivers from this page: http://www.nvidia.com/object/unix.html
For 32-Bit, run command
For 64 bit,
wget http://us.download.nvidia.com/XFree86/Linux-x86_64/290.10/NVIDIA-Linux-x86_64-290.10.runUsers with Intel and ATI chipsets can download their divers from http://www.intel.com/support/graphics/sb/cs-010512.htm and http://support.amd.com/us/gpudownload/Pages/index.aspx . After the downloads are complete, install the divers using either ./driver-file-name.run or sh driver-file-name.run command. You may have to make the files executable first using chmod +x driver-file-name . Some drivers may come in different packages. Follow the instructions in that case.
Run apt-get -f install to fix any missing dependencies and then run startx. You may want to reboot once before doing that though. startx will work just fine as intended and will guide you to he BackTrack 5 desktop.