Hello Hanspost,
If you're running 10.9, you need to reboot your machine after removing the preferences file - from my previous post:
'Nothing has changed in the FTP code for a long time, so no changes there. Weird stuff can sometimes be caused by a corrupt preferences file - you can try quitting WeatherCat, renaming your existing preferences file, rebooting the machine then launching WeatherCat and set it back up (when you rename or delete the preferences file, all settings revert back to defaults).'
WeatherCat uses the OS to talk to FTP servers (via CURL), it doesn't actually deal with the FTPing of the file - it passes the parameters and waits for the result. Most of the parameters are stored in the preferences file, you passwords are stored in the keychain, so if you still have the problem after clearing the preferences, check your keychain for issues with WeatherCat FTP passwords.