(Didn't realize sbrehm was making a response. Try his solution, it's
far easier ;-))
If the installer halts entirely, it might be somewhat of a problem. But, chances are it doesn't, so you can still access a secondary terminal to manually fix the problem.
If you are interested in fixing it manually, I'll explain how I do it here. The problem is that things might be a little different in Ubuntu, but my instructions should work with most distros.
The goal is editing the xorg.conf file to force the VESA driver. Entering a second terminal should be as easy as hitting CTRL+ALT+F2. If F2 sticks you on the same screen, try F3.
You should be at a command prompt. You can edit the file with vi. If vi doesn't work, 'vim' should.
techgage rwilliams # vi /etc/X11/xorg.conf
That should load the file to edit. You then need to scroll down until you reach a code block similar to this.
Section "Device"
Identifier "Card0"
Driver "nvidia"
VendorName "nVidia Corporation"
BoardName "GeForce 8800 GT"
EndSection
Chances are good that "nvidia" will be "nv" on your system, which is the problem. To edit, hit the "I" key, and change "nv" to "vesa". Once done, hit ESC to finish up editing. Type these two characters together, which will be displayed at the bottom, ":w" and then enter. It should say that the file was written. To exit, simply ":q" and you should be back at the prompt.
Back at the prompt, you will need to manually kill X and GDM. I don't have GDM installed on this machine, but rather KDM, but the process of ending one is identical.
techgage rwilliams # ps ax | grep kdm
2558 pts/2 S+ 0:00 grep --colour=auto kdm
5882 ? Ss 0:00 /usr/kde/3.5/bin/kdm
The first one listed is the command we just ran, while the actual executable is /usr/kde/3.5/bin/kdm. To kill it, "kill -9 5882". The program ID won't be the same on your machine, so essentially it's "kill -9 ID#".
Run the same command to see if X is running, and if it is, kill it the same way.
techgage rwilliams # ps ax | grep X
2570 pts/2 S+ 0:00 grep --colour=auto X
5668 ? Ss 0:00 /sbin/mount.smbfs //tg_nas/Volume_1 /mnt/nas -o rw password XXXXXXXX
5672 ? Ss 0:00 /sbin/mount.smbfs //wl700ge/MYSHARE1 /mnt/router -o rw password XXXXXXXX
5940 tty7 SLs+ 141:27 /usr/bin/X -br -nolisten tcp :0 vt7 -auth /var/run/xauth/A:0-4W6hvw
At this point, you can
probably start GDM again without issue, by simply typing in "gdm". At that point, you should be at a login screen or at the GNOME desktop. At this point you could probably install, as long as the entire boot process finished up.
I still find it insane that Ubuntu and others don't natively support the NVIDIA 8-series cards by default. Fedora 8 is the only recent commercial distro I have used that booted up with an 8-series card without issue. I realize this is done due to the driver being proprietary, but damn. This kind of hassle for the normal Joe would no doubt scare them off.