Re: ubuntu Failed to load the NVIDIA kernel module!
I also just upgraded to Ubuntu 9.04. My laptop has a GeForce 8200M G chip, and I was using the version 180 proprietary driver from the Ubuntu repository. After I upgraded to 9.04, the sytem would lock up after a minute or two of interaction. I've now upgraded to the 185 beta driver, and it is stable again. But it wasn't easy--I had the same problems as you.
First, in the Hardware Drivers window, remove the 180 driver. Then reboot.
When it's up again, leave the graphics screen, go to a terminal window (crtl-alt-f1), and log in. Use ps to find the X and gdm processes, and kill them.
Run "sudo NVIDIA-Linux-x86-185.18.04-pkg1.run" and follow the instructions. In my case, the tool needed to build a new kernel module. Reboot.
When it comes up, you should see a new NVidia splash screen saying "Beta driver" in red. Once in your desktop, you can configure the driver using "sudo nvidia-settings".
The reason for the errors you were getting was that the kernel module became version 185 (after install) while the driver was still version 180. You have to completely remove the 180 driver and reboot before installing the new driver.
Hope this helps.