I get logged in fine, the game runs. I try and create a new world. The world generation process starts, looks like it finishes, but when the world begins to load, I get a reticule, an inventory bar, health and food, but the screen stays black and after 20 or 30 seconds, the game crashes.

Here's the portion of the log where things start going wrong:

Client> 2013-05-03 06:42:38 [SERVER] [INFO] Preparing spawn area: 93%
Client> -3, 18, 124
Client> -5, 18, 127
Client> 2013-05-03 06:42:39 [SERVER] [INFO] megashub[/127.0.0.1:0] logged in with entity id 120 at (-175.5, 64.0, 257.5)
Client> Setting up custom skins
Client> 2013-05-03 06:42:44 [SERVER] [WARNING] Can't keep up! Did the system time change, or is the server overloaded?
Game ended with bad state (exit code -805306369)
Deleting D:\Users[user]\AppData\Roaming\.minecraft\versions\13w18c\13w18c-natives-3838676884402836
Couldn't delete D:\Users[user]\AppData\Roaming\.minecraft\versions\13w18c\13w18c-natives-3838676884402836 - scheduling for deletion upon exit

Happy to provide any other details which would be helpful.