Official Fix for "Flash Player 11 Stutters" Bug
This is not the fault of the user's system. Adobe's recommendation is to roll your Flash Player back to version 10.3 until their engineers solve this problem and issue a new (ver 12) update. To roll back to 10.3, start here:
"Flash Player 11.3 Audio Update"
and follow the instructions to do a clean uninstall of ver 11 and then install ver 10.3. This will eliminate all playback problems until ver 12 is released.
To make sure you do not let auto update reinstall the faulty ver 11, make sure you change your update settings to "prompt" rather than "auto."