When you install Adobe Shockwave 11.5 on Mac OS X 10.6 (Snow Leopard), you receive the following warning.
Press Command+I to open Applications Info for Safari (or Ctrl-click and choose Get Info).
Select Open in 32-bit mode.
The error message appears because Adobe Shockwave 11.5 is a 32-bit application, and Mac OS X 10.6 is a 64-bit operating system. For more information on 64-bit support in Mac OS X, see What's new in Snow Leopard.