[ubuntu] Fresh install question

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http://ubuntuforums.org – I've had Ubuntu for years. I'm a user, not a geek however. Updated to 12.10 a while back. Did a fresh install 2 days ago because box was running very slow. Now YouTube videos are blurry and constantly start and stop while playing. We use to have a 'ctrl+alt+del' one time to see what was going on. How can I access that now? Any ideas on why videos are now having problems? Deleted and reinstalled Firefox 18.0.1. Any info helpful, dlw (Hardware)