For awhile now I had been having issues with certain grids that, when I got near, would cause my screen to go black with 'Map data loading' for a good 2 minutes, sometimes longer. The minimap also shows black so i cannot see where my character is wandering, and unless it bumps into a tree or something, my character just keeps going. I had just started swimming a small river when the same thing happened, my character kept going into nothing but black and his stamina started draining again, apparently having walked into an unseen body of water not long after finishing his first swim.
As far as the actual bug goes, I can't find any relation to the grids at this moment that cause it, some do and some don't it seems. I can walk for several grids without a problem only to run into one that does, and i had no issues following said incident. Java and drivers are up to date.