One workaround is to use the User Switcher panel applet, instead of the Indicator Applet Session. For some reason, the Indicator Applet Session dims the display before switching; when you come back to that user's session, you either get a dimmed screen (which you can fix with "xgamma -gamma 1.0") or a completely black screen, which I've have to reboot from.
The User Switcher returns you to the main login screen, instead of the windowed user switch from Indicator Applet Session.
One workaround is to use the User Switcher panel applet, instead of the Indicator Applet Session. For some reason, the Indicator Applet Session dims the display before switching; when you come back to that user's session, you either get a dimmed screen (which you can fix with "xgamma -gamma 1.0") or a completely black screen, which I've have to reboot from.
The User Switcher returns you to the main login screen, instead of the windowed user switch from Indicator Applet Session.