Lenovo X201 tablet running Windows 7 on Active Directory requires user to login every 15 minutes. Comes up with "Ctrl+Alt+Del or use windows security button to log on" and says computer is locked. Changed default from 15 minutes in gpedit.msc to 9999. Next day it goes right back to loggin out in 15 minutes. Group Policy settings does not work.Is there a registry tweak to correct this, or another way to .change that stays.