Download a diagnostic file? Not likely :] Probably save - in which case you are getting an access violation. Check the stickied
Crashes and Diagnostic Files thread. If the access violation code you get is already on that list and is under investigation with no solution yet, you're going to have to hang in there. If it isn't, follow the instructions there to let the dev team know what's going on.
Make sure your game and graphics card drivers are updated, and that your system meets the minimum requirements, just in case.
