LTS- one forum suggested removing GTX550 card & rebooting then hotswapping....I don't think I'll do that.
Did you try this:
When the installation starts, click F6, then ESC. In the text that appears on the screen, change quiet to noquiet, splash to nosplash, and addnomodeset right after nosplash.
The install should then open. When installing check "install updates during install" and "install third party software"
For Alternate install: After base packages are installed (before grub install), open a prompt (ALT+F2) and "chroot /target", then "apt-get install nvidia-current", "CTRL+D" to exit chroot, "ALT+F1" to resume install. Complete the installation and you should be good to go.
You may also have hit a driver problem in which case:
The Nvidia 295.40 grahics driver has a bug and will not work with 12.04 precise. Nvidia are aware of the problem and are working on a fix. You can get around it however by installing the 295.33 driver which will work until Nvidia fixes the current driver. Do the following:
Go to you normal terminal and type in the following:
sudo add-apt-repository ppa:ubuntu-x-swat/x-updates
sudo apt-get update
sudo apt-get install nvidia-current=295.33-0ubuntu1~precise~xup1
On reboot it will be working. The update manager will then want to install the current version untick it to stop it from doing so and make sure your updates are only displayed and not installed automatically through settings.
Then if you haven't already done so install Synaptic Package manager and find the 295.33 driver on it you installed. Then go to settings and lock this version. It will get a little lock next to it and turn red. Now the driver cannot be updated until you unlock it. I will be keeping it locked until I am absolutely sure the 295.40 driver has been fixed.