Many times I have seen people discussing about Licensing problems and usually this happens after upgrading to a new machine or Operating System. Here is a very clean workaround shared on Adobe.com, but I also thought of sharing some information about the reasoning of this problem to set right context.
When we buy an Adobe Photoshop Elements, we get a serial number with the CD or downloaded version. Serial is important to ensure that we are using genuine software with appropriate functionality available. On installing PSE on a computer with a serial means that we have activated the serial for using Adobe Photoshop Elements on that particular computer. Till the time one serial is in full use, we can't use on extra machines. Now if we upgrade the machine or operating system and reinstall PSE with same serial, this problem occurs. So the right way of installing PSE on upgraded computer or Operating System is by deactivating the serial activation, before we use same serial on another computer.
If you are facing this problem, try following article shared on Adobe website and it should be helpful in resolving your problem. - http://kb2.adobe.com/cps/405/kb405970.html?promoid=FCSBS
Please feel free to comment back with your experiences in same regard.