Popup window on mouse hover wrongly rendered and misplaced

[igi]

Happening on Ubuntu 12.04b2, in Lubuntu Netbook sessions, after latest update of mail-notification package.
See attached screenshot for visual explanation: my lxpanel in on top of the screen; hovering the mouse on mail-notification tray icon makes its popup window to appear - partially - on the bottom of the screen.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: mail-notification 5.4.dfsg.1-5ubuntu1
ProcVersionSignature: Ubuntu 3.2.0-21.34-generic 3.2.13
Uname: Linux 3.2.0-21-generic i686
ApportVersion: 2.0-0ubuntu2
Architecture: i386
Date: Mon Apr 2 23:10:05 2012
InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Release i386 (20111012)
SourcePackage: mail-notification
UpgradeStatus: Upgraded to precise on 2012-03-01 (31 days ago)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Toutivabene (toutivabene2004)]

Hi ! Excuse my bad english...
I have the same problem on two computers : I am on Ubuntu 12.04 32 bits, kernel 3.2.0-32-generic-pae, package mail-notification 5.4.dfsg.1-5ubuntu1.
Ubuntu 12.04 installed from nothing on the first computer and was upgraded from 11.04, then 11.10 on the second computer. I use Unity on the two computers..
The popup window appears on different places. More I have messages, more the places are near the bottom of the screen. Less I have message, more the places are near the top of screen.