I know back in my Live days, people used to sometimes have this issue if they had any ports blocked within their router. (Since the patcher connects to the server <one port>, the account login screen is client side, the server select screen connect to a "different server" <different port>, then selecting the server to login to (a single one for SoD) activates client side loading...then contacts the "game server" (another different port) for your character selection.)
From your description, it sounds like you are crashing at the "retrieve character selection" portion.
Someone else will have to give you the specific info on the ports that have to be open. (I don't remember them from Live, and they may have changed for SoD.)
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Another guess, off the wall, would be your video card/drivers. (As, the character select screen is the first one to use any real graphics power...if your computer would consider SoD to be graphically intensive.)
Do you have any issues in other games that actually use 3D graphics?