Disable Overlay Scrollbars in GNOME
For Ubuntu 12.10, open a terminal and type the following command:
gsettings set com.canonical.desktop.interface scrollbar-mode normal
Changes should occur instantly. The overlay scrollbars should now be replaced with normal scrollbars.
For Ubuntu 12.04, use the following command:
gsettings set org.gnome.desktop.interface ubuntu-overlay-scrollbars false
Log out and log back in for changes to occur.