main menu on top bar doesn't appear

When opening a file with LibreOffice, e.g. text file, in Ubuntu 12.10, quite often the main menu on the top bar doesn't appear at the right sight of the symbols for closing, minimizing and maximizing the active window. Thus it is impossible to manage the file, for instance to save it with another name, to insert, format etc...
Sometimes the menu appears after a period of time, sometimes it seems to never appear. The only thing one can do is to close and re-open until the menu finally appears. This problem occurred only after having upgraded from 12.04 to 12.10, not before.
The problem is shown in the screenshot I attach to this report. One has to look at the bar where pointer is situated. Normally a menu list has to appear with File, Modify etc... but there is nothing.

ProblemType: Bug
DistroRelease: Ubuntu 12.10
Package: libreoffice 1:3.6.2~rc2-0ubuntu3
ProcVersionSignature: Ubuntu 3.5.0-17.28-generic 3.5.5
Uname: Linux 3.5.0-17-generic i686
ApportVersion: 2.6.1-0ubuntu4
Architecture: i386
Date: Sat Oct 20 11:25:12 2012
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release i386 (20120423)
MarkForUpload: True
SourcePackage: libreoffice
UpgradeStatus: Upgraded to quantal on 2012-10-19 (0 days ago)