Double click Multiscan in Storage/Monitors, then select Multiscan:Productivity in Prefs/Screenmode and click on Use. If it works, move Multiscan from Storage/Monitors to Devs/Monitors and save the Screenmode prefs.
If it does not work, reboot, double click VGAOnly in Storage/Monitors first and Multiscan next (it's important to do it in this order). Then try again. If it works now, move both to Devs/Monitors.