[ubuntu] Two password prompts after resuming from standby

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http://ubuntuforums.org – Since upgrading from 13.04 to 13.10, I need to enter the password twice when resuming from standby. The first password prompt is the typical Ubuntu Unity one. When I enter the password, the desktop is shown briefly (about 1 second or so), then the screen turns dark again and shows me the Gnome 3 password prompt. When I enter the password there, I can continue to work with the machine. How do I turn off the superfluous Gnome password prompt? (Hardware)