It sounds like you are facing a permission issue with your licensing information. What operating system are you using on the computer which is now in trial mode? Do you have any other Adobe software installed on this computer?
As Jeff said, something is messing with your licensing system. Either it's a genuine permission issue or another software on your system is interfering, which could be anything from an overly keen virus scanner to some exotic freeware program that has replaced a critical system DLL. Anyway, you did provide zero system information, so this is not even beginning to go anywhere. Check the things I mentioned and then come back with more details.