Hi
Ok, thats a nasty little problem, I've checked the machine ID and license and that is all as it should be, I think that something has happened to the windows files system, either in the 'user.config' file xml root or the JBP.exe file has been corrupted somehow, ok so lets fix it...
You will need an internet connection on the JBP PC...
With JBP closed, download this software tool to the same PC that JBP is installed on:-
http://jukeblaster.com/forum/index.php?topic=417.01. Open the tool and select 'Juke Blaster Pro' from the drop down box (top left).
2. click the button 'Try to DELETE User.Config file' (and select yes to delete any files it finds), then close the software tool.
Now try to run JBP, you may be asked to 'Register' again, just input your serial number.
If the above fails, please re-install JBP and try that...