I found this on the PropellerHeads FAQ page:
This alert may appear on Intel Mac computers when attempting to launch Reason 3.0.5.
For some reason the permissions on the ReWire folder might be set wrong. Here's what you should check:
Go to the Rewire folder (/Library/Application Support/Propellerhead Software/). Right-click on the ReWire folder and select "Get Info". Ensure that the folder permissions are set to "Read & Write".
If that doesn't help, delete and trash the folder
/Library/Application Support/Propellerhead Software/
and the two files
/Library/Application Support/REX Shared Library
Now, relaunch Reason and the folder and files mentioned above will be created. Please quit any ReWire host application before launching Reason after deleting the files mentioned above, as Reason needs to run stand alone for proper versions of the files to be created.
Let us know if that helps.