How to change QuickTime streaming settings:
In the movie window, left click the down arrow or right click anywhere in the movie window.
Next, select "Plug-in Settings..." in the context menu that opens.
Finally, under the Streaming tab, ensure that Streaming Speed is set to "Automatic". Close the settings window and reload the transcript you wish to view.
If you continue to have difficulty playing media, you may need to manually set your connection speed. Follow the above steps, but instead of setting Streaming Speed to "Automatic", try "256 Kbps DSL/Cable" or lower. Continue testing different streaming speeds until the media is able to be played smoothly.