I have the same problem! Please help!
Easy-PhotoPrint -program is also for Mac and .smi is supposed be self-mounting image. But it doesn't mount!
I tried almost everything: DiskMounter, DiskUtility, Stuffit, Toast 7, I've renamed it to .bin, smi.bin., .iso, I tried to mount it in classic (with DiskCopy) - nothing helps!
Only conclusion seems to be that the file is corrupt originally - it's from Canon's official site! Why the heck couldn't they put the usual .dmg-file?
Any suggestions?