If you have downloaded the trials there is a few extra steps you have to take. i did it with light room just the other day and its not to hard. Fallow this link and read everything carefully. its a little confusing but it works, and just google or you tube for serials, also some people put some in the comments of the video.
http://machacks.tv/2009/01/28/stop-adobe-cs4-calling-home-to-mother-ship-in-os-x/
make sure to read comment 249 because he tells you how to do it much simpler.