I don't have the slightest clue why this was causing it to crash, but going into sub object mode of your shield, selecting the element and hitting autosmooth under smoothing groups fixed it here. Everything else I tried resulted in crashes or Max not responding.
Also, I used the STL check modifier and you have an open seam along the top of the shield you might want to weld shut...
3ds Max 2009 SP1, 2010 SP1
Maya 2012
Windows 7 Professional 64-bit
Dual Intel Xeon E5520, 6 GB Ram
NVIDIA GeForce GTX 460 OC