[Adobe Flash] Playing of flash-based videos is laggy

Playing of videos, for ex. on YouTube, is laggy. When you try lower video resolutions, it's a bit better but sometimes even then there is lag and some frames are skipped.
I also tried to play videos on YouTube in Google Chrome but the situation is identical.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: flashplugin-installer 11.2.202.236ubuntu0.12.04.1
ProcVersionSignature: Ubuntu 3.2.0-29.46-generic 3.2.24
Uname: Linux 3.2.0-29-generic x86_64
ApportVersion: 2.0.1-0ubuntu12
Architecture: amd64
Date: Sun Aug 12 12:53:16 2012
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64 (20120425)
ProcEnviron:
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: flashplugin-nonfree
UpgradeStatus: No upgrade log present (probably fresh install)