Flash content shines through black background of other windows

[Lars Volker]

When hardware acceleration is enabled, flash content shines through any black pixels of other windows, that are moved in front of firefox. A year ago the same issue was discussed here: http://ubuntuforums.org/showthread.php?t=1720001
Is this a regression?

I know that the combination of nvidia restricted drivers and adobe flash probably disqualifies this as an ubuntu bug, but I don't know where else to ask and think, that other users might have the same issue as well.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: flashplugin-installer (not installed)
ProcVersionSignature: Ubuntu 3.2.0-24.39-generic 3.2.16
Uname: Linux 3.2.0-24-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.0.1-0ubuntu8
Architecture: amd64
Date: Sat Jun 2 18:18:45 2012
InstallationMedia: Xubuntu 10.04 LTS "Lucid Lynx" - Release amd64 (20100427.1)
ProcEnviron:
 TERM=xterm
 PATH=(custom, user)
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: flashplugin-nonfree
UpgradeStatus: Upgraded to precise on 2012-06-02 (0 days ago)