Restart Videopad. If you cannot close it, try this...
Press the <ctrl-shift-esc> keys simultaneously to bring up the task manager.
Click the PROCESSES tab and then scroll the list at the left, using the scroll bar at the right, until Videopad is seen.
Right-click on it and END TASK.
Restart VP. Remember to back up your work periodically with an incremental name, so as not to overwrite earlier backups.