Have you tried the downloading and manually installing drivers? Fair warning: This is a pain to maintain yourself. This is how I was able to run 10.04 LTS for several months. My NVIDIA card (a GeForce GT430) was never detected. As a last resort, this worked great. As I type my video card now fine in 12.04... But, it never worked in 10.04 no matter how much I tried until I did this.
1) Download the newest drivers here:
IMPORTANT: Keep these in a safe place in your home folder! Every time you update the kernel you will need to run the installer again. What happens is, every time Ubuntu auto updates the kernel and reboots, it complains and gets stuck. Don't panic. Simply drop to a console and run the installer again (Steps 6, 7, 8, and 9) when this happens.
2) Open module blacklist as root:
gksudo gedit /etc/modprobe.d/blacklist.conf
3) Add these lines to the bottom of the file and save:
4) Uninstall any previously installed Nvidia drivers:
sudo apt-get --purge remove nvidia-*
5) Reboot your computer
6) When an error message pops up saying that Ubuntu cannot load Nvidia drivers, choose Exit to terminal (Exit to console)
6b) If it boots without error, try Ctrl+Alt+F1, login as yourself,
sudo service gdm stop
7) Install drivers (change REPLACE_ME accordingly):
sudo sh NVIDIA-Linux-__REPLACE_ME__.run
8) Answer the questions in the installer, follow-through, exit.
sudo shutdown -r now
PS: To uninstall, if ever, it's
sudo sh NVIDIA-Linux-__REPLACE_ME__.run --uninstall