Open a command prompt at \..\Creo 2.0\Parametric\bin (hold down the shift key and right click the folder in windows, select open command prompt here). Type ptcstatus. Look for your user name and find your port (i.e. 7788) and handle numbers as well as the feature and license server.
Then type in another command window or the same: ptcflush [feature] [license server] [port] [handle]. The license will be released.
Sounds like you need to adjust the timeout (or whatever it's called) for the licenses.