Yes I have a LOT of other Steam games.
LoL, heheh... me too.
So (to be clear) there's nothing wrong with Steam for you guys - it hooks up, and you can play other games okay, right?
But just the New Vegas title, it says 'game not available at this time' - wtf is that?
It seems like it could be some kind of weird verification system that's glitching you...?
I mean, the files are all right there on your harddisk (just like FO3) but if you try running it without Steam it doesn't work. So it must be going to Steam to authorize you when you first fire it up.
Sometimes authorization problems can occur if you have a wireless internet connection (or even a wired one) that is many hops removed from the internet, behind multiple NAT firewalls or proxy server(s).
Also, some CDs and DVDs install software that will remain on your system, and disable certain programs used to rip CDs and DVDs, and wreak havok on your general DVD funcionality and also many kinds of authorizations/verifications.
For example, you might be attempting to play the game on a Teenager-PC that is running filesharing and torrents, ripping DVDs and Blurays, burning stuff of dubious heritage, etc...
Codecs flyin' left and right, Windows in rough shape, infected with this & that. Messengers, updaters and all kinds of bloatware running while you're trying to start this game.
Not saying this is you!But all these types of things can be factors when struggling with updating/authorization/verification issues over the www.
Also: you might go into Optional updates in Windows Update, and update your Root Certificates and any other updates referring to security and authorization/verification compliance.
But I'd be upset if I were you.
Good luck (hope something/anything helps!)
Regards