I just bought it on Steam and it won't start. I can go into the steamapps folder and launch it myself, but then it doesn't work with achievements and everything within steam. When I try launching it in Steam it pops up the window "Preparing to launch Dungeons of Dredmor..." but it never launches. I've left it for at least 10 minutes. I've tried deleting and reinstalling the game and even deleting the folder in My Documents, but still nothing. Any ideas? Thanks.
The few times I had this problem I simply restarted my Computer and booted Steam up fresh, and away I went. I know that's not terribly helpful but perhaps if it does it again, try closing Steam completely (use TaskManager if you have to to kill Steam.exe) and "rebooting" it. Steam is just wonky sometimes and needs a good smack upside the head.