This can happen if Replay Media Catcher's data files become corrupt. Here's how to re-create the database files:
1. Close Replay Media Catcher
2. Remove this folder:
Windows XP: C:Documents and SettingsApplication DataReplay Media Catcher 4
Vista/Win7 C:UsersAppDataRoamingReplay Media Catcher 4
3. Restart Replay Media Catcher and the files will be re-created.