I have installed the latest update (11.2.202.228 or 11.2.202.228-0natty1) of adobe-flashplugin and found that video colors are not natural but give kind of inverse color shift, e.g. faces (in youtube videos) become blue. My computer has Ubuntu 11.04 Natty 32-bit OS with 2.6.38-13-generic-pae kernel, and Nvidia GeForce GT420 video card (driver version: 290.10). I have solved the problem by reverting to previous plugin version (11.1.102.63 or 11.1.102.63-0natty1). The previous plugin version you can find in /var/cache/apt/archives directory. To check the flash plugin version, open your web browser and go to http://www.adobe.com/software/flash/about/ Archived Flash Player versions are located at http://helpx.adobe.com/flash-player/kb/archived-flash-player-versions.html
The flash player 11.2.202.228 version addresses critical vulnerabilities in Adobe Flash Player 11.1.102.63 and earlier version, see details at http://www.adobe.com/support/security/bulletins/apsb12-07.html
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Reverting to previous flash player version seems a bit more complex because the newest Google Chrome (version 18.0.1025.142) installs own flash player (libgcflashplay er.so) ... and as you may guess ... it is notorious version 11.2.202.228. I solved the problem by copying and renaming previous version:
$ sudo cp /usr/lib/ adobe-flashplug in/libflashplay er.so /opt/google/ chrome/ libgcflashplaye r.so