This is a kernel bug <https://bugzilla.kernel.org/show_bug.cgi?id=42876> which says that all 3.2 and 3.3 kernels will crash as soon as the nouveau kernel module is loaded. I don't know if other NVIDIA cards of the NVC0 generation are affected as well.
The good news, not noted in the upstream bug: the issue is resolved in 3.4rc2 at the latest. Verified on Fedora 16.
Ubuntu 12.04 is already in the kernel freeze phase prior to the release, so the OOTB experience will likely remain broken for all users with a GTX 550 Ti. The workaround is to prevent nouveau from loading and to use vesa instead.
It has been reported that a bug in the nouveau video driver causes systems with an NVIDIA GeForce GTX 580 video adapter to hang as soon as the X graphical environment starts up. This issue also affects installation, so as soon as X is started, installation hangs.
This issue can be worked around by disabling hardware acceleration. To do this, pass the kernel parameter nouveau.noaccel=1. You can append kernel parameters at boot time - of a live image, DVD or network install image, or an installed system - by hitting the Tab key when the system reaches the bootloader menu, and typing in the desired additional parameter.
You can make the workaround 'permanent' on an installed system either by editing it into the /boot/grub2/grub.cfg file, or by creating a file named /etc/modprobe.d/noaccel.conf containing a single line reading:
options nouveau noaccel=1