The FAL

[-{ET}-xdEpicZombie]

This is a known bug with Milkshape.It mostly crashes becouse the mesh has to big polycount.Heres what You do:always save Your model(not export but save,in milkshape to ms3d file),finish your animations and save again(saving here is important),now make a quake confiq file(It must be in the same directory,with the same name that Your exported file will be),now export Your model to .md3.Even if Milkshape crashes during the export,the funny thing is that it actually exports the model.The saving before exporting is important becouse If You are trying the model ingame and You dont like something about the animations or anything else,You could still open Your model with animations(usually when yhe model has too many polygons and it crashes during the export to md3,You cant import the model also-as I said,saving there is very important)
Hope it helped!!