Fallout: New Vegas Discussion
I don't use steam, I always crack mine after I install so I don't use it, saves a lot of headaches when my internet gets "Special".
I can't offer much advice that would help but I'll try
As for your problem, I don't think you're doing anything wrong. once you hit the tilde (~) key the game should freeze, nothing will appear like a window or anything like that but as you type you'll see what you type at the bottom or near the middle of the screen.
Although the problem itself could be steam, the damn thing has a mind of its own, it has anti-cheating crap as well I think, that itself might be preventing you from cheating in your games, though it should only be active if you're playing multiplayer, it shouldn't do anything if you're using single player games like fallout new vegas or similar games.
If you'd like I can pm you ways to... circumvent these things.
* Updated game trainers and cheats daily
* Get notified when new cheats are added
* Request which games get new trainers
* Priority support with any problem