I have been having the exact same problem since I updated to 1.3.0.4, but not in previous versions. After about a half an hour of playing my game will freeze for about a second and then instantly shut down, with steam subsequently crashing as well. What i'm doing in game doesn't seem to be a factor as it has occurred while doing anything from killing crimson enemies to mining desert fossils.
The game has also crashed a few times whilst saving and exiting, and loading worlds, with steam also crashing in this situation as well.
This has been happening to my installation of Terraria as well,
and only since the .4 hotfix.
At first I figured it was only happening on certain world seeds, but no matter how many worlds I generate, they always either crash after playing for a while OR when exiting the game - it seems to write the savefile correctly and uploads it to the Steam cloud, but
then it just crashes to desktop, taking down the Steam client in the process.
The game also crashes when moving from a pre-1.3.0.4 world to a new world, generated after the latest hotfix, 100% guarantueed. Starting Terraria and immediately going to a new world will work fine.
At first I figured it had to do with cloud-saving (since it mostly crashes when either saving the data or accessing a world on loading), so I generated a new world without moving it to the Steam cloud, played around a bit and then exited the game, with the result that the game immediately crashes on exit while writing the local savefile. So it makes no difference whether the worldfile is stored locally or externally.
The only exceptions I've noticed:
- Enter a world for a very short time and immediately exit - it will shut down just fine
- Both of my pre-1.3.0.4 worlds seem to be doing fine and I can switch between them as often as I want
- Randomly, Terraria will shut down gracefully, even when having played for more than a hour
So... Rollback to 1.3.0.3 please?