I'm sorry to hear about your problems with New Vegas,
Arwen.

I've had the same problem with Steam before as well, usually with TF2. I find it seems to fix itself either after I restart steam, or if I change my download location (say from somewhere in America to like Australia or something). It's not a problem with Steam, but with the servers usually. They tend to be quite stupid, for lack of a better word.
What's with these updates that require modders to update their mods? I mean, what's that all about anyway?
Well, in NVSE's case, the versions that are out require a certain version of the game's .exe to work. And seeing as all game updates update said .exe, it makes NVSE incompatible with the latest version. All other mods don't require this, so they should function fine. The only mods I'd be concerned about are the ones that change weapon values and such (like this one) or ones that introduce various bugfixes. And the gun concerns only stem from this patch so far and no others.