I've just had a similar nightmare in UDK for the last 20+ hours. At first, my tree models were loading okay but they weren't painting in the terrain editor properly. Then, the textures were getting corrupted or something and every time I tried to save the package, UDK crashed. I have gone through this about 100 times now.…
This might not be the cause but, under the hood Speed Tree makes a check to see if the Speed Tree that you are importing has more than four Material ID's. If your Speed Tree does have more then four Material ID's then the Speed Tree import code will automatically reduce that number to be under four. However it seams that…