For some reason, I re-installed Ubuntu 14.04 on my computer. But this time, I detected a glitch on boot. After the motherboard boot finished, there's a black screen with a purple border, and then for a short amount of time a black screen appeared with a single vertical glitch, and then the purple Ubuntu loading screen appears. That's the only odd thing, but I've never seen such a thing in the previous installation, so I'm worried if something went wrong in this install. After installing Nvidia proprietary driver, the behavior is still the same.
My graphic card is GTS450, and my screen is 1920x1080 connected in HDMI.