I am running version 8.0.5.7 an the authentication works, but when I restart my computer and run the program again, it states the system is demo version only. I can authenticate again, but concerned this error will continue. It has occurred 5 times already.
The only thing I can think of right now is that somehow your registration does not persist. As far as I do know it's written to the Windows registry -> HKEY_CURRENT_USER\Software\eXtremeMovieManager8\MyKey ... maybe some other software deletes the entries regularly. Like some kind of a "registry cleaner"?