Be sure you have the most recent version of the Real Player

MAC Users
  1.  Open Internet Explorer's web browser.
  2.  Go to the web browser's Properties menu.
  3.  Select the Protocol Helper option.
  4.  Scroll down the list until finding the Real-Time Streaming Protocol (RTSP).
  5.  Change the application type to RealOne Player or RealPlayer, depending on which application you have downloaded.
  6.  Close and exit the browser and then reopen and try a video link.

RealOne Player (Build 6.0.11)
PC Users
  1.  Click on the Start menu button on the Windows' Taskbar.
  2.  Go to Programs, then Real, followed by RealOne Player.
  3.  Once the player launches, click on Tools.
  4.  Click on Preferences.
  5.  Click on the Hardware category.
  6.  Under Video Card Compatibility, move the slide bar from its right position to the middle.

MAC Users
  1.  Click on the Apple Menu button and select RealOne Player from the list of applications.
  2.  Follow steps 3 to 6 above.

MAC Users
  1.  Click on the Apple Menu button and select RealOne Player from the list of applications.
  2.  Follow steps 3 to 6 above.

RealPlayer 8 or earlier
PC Users
  1.  Click on the Start menu button on the Windows' Taskbar.
  2.  Go to Programs, then Real, followed by RealPlayer.
  3.  Once the player launches, click on View.
  4.  Click on Preferences.
  5.  Click on the Performance tab.
  6.  Uncheck the "Use optimized video display" box in the Video Card Compatibility section.