Lubuntu automatically closing programs when locking computer

[Numa_slk]

I have just installed Lubuntu on on my Toshiba Satellite. it works fine. But whenever I lock my laptop pressing ctrl+alt+del and then unlock it, I find that all my opened programs have been closed. How can I fix this?

~$ cat /etc/*-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=14.04
DISTRIB_CODENAME=trusty
DISTRIB_DESCRIPTION="Ubuntu 14.04 LTS"
NAME="Ubuntu"
VERSION="14.04, Trusty Tahr"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 14.04 LTS"
VERSION_ID="14.04"
HOME_URL="http://www.ubuntu.com/"
SUPPORT_URL="http://help.ubuntu.com/"
BUG_REPORT_URL="http://bugs.launchpad.net/ubuntu/"

[bapoumba]

ctrl-alt-del logs you out of your session (I tried it ) and ctrl-alt-l the L letter) that is supposed to lock the screen does not work : https://bugs.launchpad.net/ubuntu/+s...n/+bug/1286686