I am new to Ubuntu. I was trying install Ocelot(to run CUDA simulations without a GPU) and was following these instructions(https://www.udacity.com/wiki/cs344/llvm_ocelot_dev). There was a power cut here and since my laptop does not have a battery the installation got interrupted. The next time I tried to log in, the panel was missing. I could not see anything other than the desktop wallpaper. I updated the version from 12.10 to the latest version using ctrl+alt+f1 shortkeys. I tried several solutions already posted in various forums without any result.