Sidebar and menu bar suddenly disappear from screen

While surffing the net with no video or audio application running, both menu and side bars disappear. Terminal wo'nt open as well using CTRL+ALT+T.
Tty terminals open normaly.

a : sudo restart lightdm reloaded the desktop and everything returned to normal. It has happend to me twice at least during the last 5 days. Using Ubuntu 13.10 for about a week now.

Thanks.

ProblemType: Bug
DistroRelease: Ubuntu 13.10
Package: bamfdaemon 0.5.1+13.10.20131011-0ubuntu1
ProcVersionSignature: Ubuntu 3.11.0-12.19-generic 3.11.3
Uname: Linux 3.11.0-12-generic i686
ApportVersion: 2.12.5-0ubuntu2.1
Architecture: i386
Date: Sat Nov 2 18:19:34 2013
InstallationDate: Installed on 2012-12-17 (319 days ago)
InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Release i386 (20111012)
MarkForUpload: True
SourcePackage: bamf
UpgradeStatus: Upgraded to saucy on 2013-10-26 (7 days ago)