If you get on a horse and ride far enough to require the game to load unloaded chunks they chunks will not load properly. Most of the time when you dismount the chunks will immediately load. Sometimes dismounting will not load the chunks and you must logout / login again to correct the issue.

http://i.imgur.com/vTNcFkL.png

http://i.imgur.com/U62jW40.png

Though I have not tested this in anything but my survival world with the one horse I have, I am able to replicate this issue every single time I get on my horse and ride past the currently loaded chunks.