Here is the simple way to fix this error.
Find this folder in your system drive
/Library/Application Support/Adobe/Adobe PCD/cache/cache.db
The above path refers to the top level Library immediately inside your Apple Mac OS X hardrive. Now when you restart your CS4 apps you’ll be prompted to license your product with a new serial number.
If you have lost your serial number / product key, or otherwise feel justified in so doing, you may download a CS4 keygen (key generator) which will work on your Mac (PPC or Intel based) here. (download it, erase .html at the end of the document name and unrar it)
If the Adobe activation servers are stopping you opening CS4, see Simple way to activate Adobe CS4 infamous activation permanently for Mac OS X