Have you tried this in another user account on your MacBook ? This will help to narrow down the problem to user specific or System wide.
Just for clarification sake, did you uninstall/re-install Flash as per the instructions at this website?
Installation problems | Flash Player | Mac
Another thing you could try is to boot your Mac in Safe Mode Restart and when you hear the chime, press and hold the Shift key.
Mac OS X: What is Safe Boot, Safe Mode?
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Safe Mode is a stripped down version of your operating system. It can allow you to get into your computer and troubleshoot, or save documents, when your normal operating system won't boot up. It's very simple to start your Mac in Safe Mode. With the help of this quick how-to guide, you will be well on your way to recovering those documents!
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