Mmd Help!!

I'm not familiar with the program, but I've encountered similar when using Blender. Is this happening on export? If so, it may be that what you have, while it works, is too much for the format (or for your computer in attempting to convert so much into that format). Sometimes programs can also conflict with each other (I've found this especially true when graphics cards are involved) so make sure that's the only thing you're running. I could do some searching if you still need help.