Lol it happens so randomly that its all over the place, and if it was only ever mission 3, then i wouldnt care much and id save every 1 min and keep going xD, but sadly, it happens on 1 and 2 as well, tho rare. Im sad to hear its not something your able to effect, but cant be helped. And as to what im doing when it happens, im simply building my base, my units are securing the area around me and pushing the fog of war back to the cliff line south of the nod base. Sometimes i get right to the nod base before a crash, sometimes im still on my side of the cliffs. Its very random.
Oh and yes im using cncdraw, windows 7 64bit, 16gb ram, 4gb graphics card, intel core i7-4790