Weird error where textures get really simple at random times

I am having a strange error I’ve never encountered before. The map is currently in the very basic W.I.P stage and not much at all has been completed. It probably takes less than a minute to compile, so it can’t be anything to complicated and obscure. While testing, the textures in the map will go from being detailed, to randomly turning to a simple color or something. Some images as examples.
The textures will shift from this:

http://img828.imageshack.us/img828/9852/ggminorthreatwarehouse0.jpg

http://img718.imageshack.us/img718/9852/ggminorthreatwarehouse0.jpg

To this:

http://img210.imageshack.us/img210/9852/ggminorthreatwarehouse0.jpg

http://img685.imageshack.us/img685/9852/ggminorthreatwarehouse0.jpg

I noticed that all of the textures with transparency like trusses and support beams disappear. Notice the windows and the layer of trusses vanish.

Looks like the draw distances on your computer, increase your settings so it doesn’t do that if you can.