Ubuntu 12.10 Login screen doesn't show background

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http://askubuntu.com – I own two laptops, and upgraded to Ubuntu 12.10 on both of them. On one of them, when I get to the login screen, I see a nice interface with the same background image as the desktop, and a nice transparent widget that asks me to choose a username to login. However, on the other laptop, the b/g image is just gray and the login screen doesn't look as nice. The widget seems different too. Any possible reason this might be happening? (HowTos)