I had a similar problem not to long ago, except that it tried to get past the purple screen and just got this terribly distorted black picture. I could not get a working desktop, but I was able to get a working desktop booting with nomodeset. It was a fresh install, so I knew the system had been installed, and I could not get to it due to something going wrong with the video drivers.
Step 1: Involves you going to this website and reading the part that is labeled "Black/purple screen after you boot Ubuntu for the first time". Use this part to hopefully get a working ubuntu desktop or atleast something close to it.
If you are able to get a working desktop awesome, if you end up just getting the background (other than purple) try opening up a terminal window with Ctrl + Alt + T.
Type the following code to install the nvidia drivers for our video cards(I happen to have the same exact one)
After this, all I did was reboot the computer, in the case that you are stuck in a command line environment, this should do the trick:
sudo apt-add-repository ppa:ubuntu-x-swat/x-updates
sudo apt-get update
sudo apt-get install nvidia-current
Once everything is done, you *should* have a working desktop.