@ Dark_Wolf_of_Courage
It might be of use to have two things in order to fully understand your post.
The first one:
When that area you say appears as black, but renders ok "far", use the /pos command.
Just type /pos on your chat box and hit enter. It should return you the position you're in and the map name.
The second one:
Take a screenshot, just so it can be seen with a picture, what you describe. It might be related to a graphic hardware/driver issue (you should also post your system specs while you're at it) but having a screenshot always helps. To have one, just switch to system tab, and type /screenshot on your chat box, then hit enter.
If all went fine, you'll have a screenshot of the map location with your issue, and the system tab will contain still the position you're in, so you'll save that typing.

You just need to go then to
www.imageshack.us (or similar image hosting service) and upload the screenshot you just made (to be found on planeshift screenshots folder, typically program files/planeshift/screenshots) simply put a link to the image in your next reply, together with those system specifications.