Tom,
Slew up to about 2,000 feet AGL and pan around Misty's. Is the ground still black? You mention that when taking off, the water in the canal looks OK, and when you reach the lighthouse the water turns blue. What does the water look like when you slew up and pan around? My initial guess is that your ground textures are very slow to load for some reason.
Another thing to try is to go to the FSX settings/graphics menu, wait a second, and then exit back to FSX. Does it return immediately, or does it sit there and "think" for a while? If it sits and "thinks", and then returns to FSX, does the ground look normal now?
Steve