Probably just a temporary conflict, preventing access to the PDFE database files. If it happens again, try to discover why these database files aren't accessible to PDFE.
In this situation is also recommendable to check if an unfinished, and hidden, PDFE instance is active, using the Windows task manager. Kill it before start PDFE again.
But I need to get ride of that exception that showed after that generic "Error creating Database" error message.