It is possible you somehow messed up the logbook file, though I have successfully deleted, copy/pased, etc into it before.
Just delete the file and start over again. If two files end up on the same day you can remove (inside the program) both of them, then do "add all files to log book" with only the file you wanted for that day loaded. We hope to have a better way to handle multiple files per day soon.
Post again if you're still having problems. There could be a problem that needs a further look.