I recently ran into this bug when installing the Nvidia video drivers on Ubuntu 9.04 64bit Desktop.
The restricted drivers window hangs on "downloading and installing" and eventually presents a screen saying:
Sorry, the Jokcey backend crashed. Please file a bug at:
Trying to recover by restarting backend
We can install the restricted Nvidia driver for Ubuntu without using Jockey.
Read on to find out how!
1) Install nvidia drivers
# sudo apt-get install nvidia-glx-180
2) Run nvidia config
# sudo nvidia-xconfig
Reboot and you should be running the restricted Nvidia driver :)