What you need to do is go to your installation directory and run the "meter" program. This program will tell you how many decodes you have left on your USB key and what the expiration dates are.
By the message you posted it looks like you have run out of decode capacity on a demonstration key. Could this be the case?
Again, run the C:\InstallDirectory\Decoder\Meter.exe program to find out what is left on your USB key.