It's a vertices error. Most common error model editors run into once or twice. You went over the vertices limit in PMDeditor to whatever item was grey, and that item glitched out the model. Either convert the model to .PMX, since .PMX models can handle somewhere over 10,000 vertices, remove the item and re-add it, but save the model as a .PMX, or start over and add all the items to the base again, but be sure to save the model as .PMX this time.
I have version 8.03 and version 9.02. The glitch I found, happend with version 8.03. In the newest version I didn't find any glitch already. Maybe it's better you try the model on the new version (But on the new version it doesn't work MME)
When I found this glitch I remember that my MMD was always closing. Then next day I tryed to open the model and it worked. Maybe you need to restart your computer. If that doesn't work you can try to DL the model again.
using mmd or another software?
You have to select MikuMikuDance (DirectX9 Ver.) (I noticed that the version now is 9.08)