In terminal as root try doing: Code: apt-get install system-ui-screenlock-nokia --reinstall Reboot and try...
apt-get install system-ui-screenlock-nokia --reinstall
~ # apt-get install system-ui-screenlock-nokia --reinstall E: Could not get lock /var/lib/dpkg/lock - open (11: Resource temporarily unavailable) E: Unable to lock the administration directory (/var/lib/dpkg/), is another process using it? ~ #