I have been using PS CS4 for more than 3 years. However, in the past few months, PS CS4 keeps popping up Error:150:30 indicating Licensing for this product has stopped working.
When this error came up, I used to closed and re-launch the program or restart the computer and the error will go away. But not this time. I have been trying to used CS4 for the past few days and failed.
You don't state what operating system you are using.
Here is a solution for Mac: http://helpx.adobe.com/x-productkb/global/error-licensing-stopped-mac-os.html
Hope this helps!