Looks like your SDL framework is too old (either you have a PPC version that's not Intel compatible or an early Intel version that's 32-bit while your machine is now 64-bit). Trash your /Library/Frameworks/SDL folder and download and extract the latest as described:
Go to http://www.libsdl.org/
, and click the "SDL 1.2" download link in the sidebar, then scroll down to "Mac OS X" under "Runtime Libraries". Download the "SDL-1.2.14.dmg" disk image and open it.
Click 'Macintosh HD' (or whatever your Mac's hard disk is named) in the left pane of a Finder window, then open the Library folder and drag the SDL.framework folder from the SDL disk image into the 'Frameworks' folder.