Minecraft preview hangs or crashes near plain coloured banners

Preview works fine unless i am near plain coloured banners. The graphics sometimes freeze (but the game is still running, and will save itself in the background if left alone) . Other times the game crashes, i think this happens if it is about to update the save. Neither the crash nor the freeze happen if i am more than about 50-100 blocks away. The freeze will usually happen almost instantly if i walk into a room with banners.