an unexpected error occurred (error code -10822), when trying to install Adobe Photoshop in my Mac... what does it mean? Thank you :-)

Hi ALL!

I am trying to re-install Adobe Photoshop in my Mac Mini OSX 10.5.8 since for some reason the one I used to have stop from working. Now when downloading it from the Internet it always says "an unexpected error occurred (error code -10822) after I open the icon. What does it mean? How can solve it? HELPPPP!! Thanks... :-)