Are you using the regular Feral Heart or Feral Heart+?
If you're using Feral Heart+ this might help (although you should stop using it altogether):
http://www.feral-heart.com/index.php?option=com_jfusion&Itemid=2&jfile=index.php&topic=13593.0
On the other hand if you are using the regular Feral Heart did you uninstall the game but also
delete the Feral Heart folder before reinstalling? To really be sure that you clean out any damaged, missing, or misplaced files that could be causing the black screen problem you need to do that. Be sure that you have any important files like presets etc backed up though.
If that doesn't work try doing a character reset from the top right of the forum in case your character or characters are stuck on some long gone map that you deleted while uninstalling your game:
Character Reset

If that doesn't work you could try messing with your game's video settings if you can get to the main menu. Click where it says "options" on the main menu then "video" from there set your settings like so:
-Switch your rendering subsystem from OpenGL to Direct3D9
-Turn Water Reflection Off
- Put View Distance to 0
I hope something there helps. Good luck