Lowering the color depth for the X server is not a great workaround. It seems that the ubuntulooks engine is buggy, so I modified the Human theme gtkrc (/usr/share/themes/Human/gtk-2.0/gtkrc) to use the clearlooks engine instead of the ubuntulooks engine, and all is well -- I have a visible progress bar now.
This workaround could be applied to any other theme that uses the ubuntulooks engine, including Outdoors and Silicon. -- Progress bar is invisible https://launchpad.net/bugs/67443 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
