Mod veiwer is known for buggn out from time to time. There are several things to try:
restart mod veiwer.
if model is on CD, put it your hard drive.
restart windows.
check to see what format the textures are, see if there 256 or 16million.
any of these things could cause a simple miss hap.
I had a ship in mod veiwer once that looked just like that, the problem was that there were 2 meshes in one, kinda like an LOD, except they were the same model & size, just off set slightly. Imported to max & deleted 1 of them & it was fine.