adb and platform-tools not working anymore on Mac Lion
Hint, Google repository. Ah here you go a better example from the past


Find your Sdk folder then locate both tools and platform-tools subfolders. 
Check the Google repository  find what version you want to downgrade to and download the .ZIP for both.
Unpack the the .ZIP's you just downloaded move the Tools subfolder over to your Android Sdk folder. Then move and extract the Platform-tools subfolder to your Android Sdk folder.


Now you should be good to go.