Helps to get rid of low textures, is the fast camera rotation a bit from side to side or (but not 100%-camera zoom right mouse button). This started happening in the 0.62. Before 0.62 I dont have such big problems with not loading textures.
I heard that this often happens on laptops but on the PC too.
Texture quality set at high. (sorry my english is not very)
Here are just a few examples, before and after fast camera rotation from side to side: