As far as I know, Network Magic is an application that has been discontinued without any possibility of using it anymore. The problem is related to activation, and since you can't reactivate it, certain functions won't work properly. I recommend using something else instead of Network Magic.
As alternative with better support options and features, SpiceWorks can do the job really good. Give it a try through the following page: http://spiceworks.software.informer.com/
Note: Click on the download button to initiate the download.