gonzo were you using a mod from 1.02? I have had the same problem but I found that there is a single line addition to the ship,starbase and planet entity files that might be the cause. ie
between entrenchment 1.02 & 1.03 of adding a line
renderShield TRUE
after the shieldmeshname line.
since I added the rendershield line into the entity files(by hand a fairly slow process) I had a 5 hour game without crash.
hope this helps
harpo