On my desktop, whenever I try to install a new version of ubuntu, the live CD/USB Drive boots up with a GUI that's scaled for my resolution (1440x900), but the pixel size is two or three times the size it should be, making it hard to read text and just plain ugly. I have encountered this with at least five different versions of ubuntu, installed on various flash drives and DVD's. The checksums are fine on all of the images I've tried. I have gone through with the installation a few times and the resolution graphical glitch persists into the installed system (regardless of what the resolution is set on) until I install the proper Nvidia Drivers. When they are installed, I have the proper resolution for my monitor but it is much slower (in terms of framerate in games) than it should be. I managed to get get a good install of Kubuntu 15.04 on this desktop by creating the image on a fresh USB drive from my Lubuntu Laptop, but now I want to switch to the LTS on the desktop and any image I create with either machine gets this pixelation bug. My laptop does not have this bug. I will test an image on the laptop and see if it does the same thing and update this post.
