If the issue IS Activation, a call to Adobe Customer Support will get that cleared up.
Congratulations on being one of the smart ones to make a CD of your original download. I would try resetting preferences first to see it that helps.
Start PS and immediately hold down shift alt ctrl keys. If fast enough you will get a reset window.
Also, update your GPU drivers from the manufacturer. Same with printer and scanner. They can be cause of problems.
If you have any thoughts of upgrading you have until the end of this December to get upgrade prices. After that you will have to pay full price. CS3 Bridge was a buggy version and so worth the upgrade. Beware however you really need 64bit and 8 gig of ram to reap all the benefits of CS6.