I ran into a similar problem with OS X 10.5 last year. The fix was obscure enough that I wrote myself a note to remind what the solution was. I copy it below and hope it helps.
June 22, 2011 David Lawrence
There was a problem running the mindstorms software on OS X 10.5 that claimed a file was broken while starting up.
I found the solution on a German website (translated by Google). The 3 steps they gave that seemed to fix the problem were:
1.) Download and install the MAC Leopard fix patch from lego (click "Patches" on the left):
2.) Download and install the Fantom Driver from the lego site (Click "Drivers" on the left)
3.) Make a symbolic link called fantom.framework that points to Fantom.framework in /Library/Frameworks:
sudo ln -s Fantom.framework fantom.framework
It seems this may be an issue with the case-sensitivity of the underlying file system. Mac OS X usesa case IN-sensitive file system by default. This was hidden from users by a layer that maintained the case of filenames separately. I chose to enable case sensitivity (which is not the default) in the underlying filesystem when last installing OS X so that Fantom.framework and fantom.framework no longer point to the same point on the disk. Step 3 side steps the issue.
I can't help but notice that there is also a VISA.framework directory there which looks like a LabView thing. It may well be that one does not need the Fantom driver at all and simply needs a similar link or renaming of VISA.framework to something like visa.framework.