With the introduction of Mac OS X Lion (10.7), Apple dropped support for Rosetta. As a result of this change, Cakewalk instruments and audio effects for Mac have been affected. As of this time, Dimension Pro, Dimension LE, Rapture, Rapture LE, Studio Instruments and the Production Packs are not officially supported on Mac OS X Lion (10.7) or greater. Attempting to install one of these products on 10.7 or higher will result in an “Invalid Serial Number” message. More information about OS X compatibility is available on this Knowledge Base article.

If you are receiving this error message on OSX 10.6.8 or earlier, please check the following:

1. Make sure you are logged into your computer using an administrator account. If you are not the administrator, the installer could have permission issues attempting to install the serial number verification tool to your temporary folders.
    
2. Repair your disk permissions
   1. Go to your Applications/Utilities folder and open Disk Utility
   2. Select your main HD within the list on the left-hand side
   3. Click "Repair Disk Permissions"
   4. After the permissions repair is complete, use the "Verify Disc" and "Repair Disc" function. (It will only allow you to repair if necessary)
       
3. Use an English language localization of the Mac OS
   1. Go to System Preferences
   2. In System Preferences click International
   3. On the first page click and drag English to the top
   4. Save the settings
   5. Log out and then log back into your account
       
4. Make sure that you have Rosetta installed on your computer. If not, it's possible to install it with these directions: http://www.macobserver.com/tmo/article/snow_leopard_installing_rosetta
    
5. If you are trying to install the full Dimension Pro or Rapture, remove any LE versions of these synths that may be installed. Please contact Cakewalk Tech Support if you require specific instructions for removing them. If you have never installed Dimension LE or Rapture LE, you may ignore this step.
    
6. Install to the same drive that contains the Mac OS. If you try to install it to an external hard drive or any other non-system drive, the installation will fail.

After following the above suggestions, attempt to install your Cakewalk software again.