So I opened up Skyrim today and it said failure to enumerate subscribed files. Which meant it couldn't check to see if my subscribed mods were up to date. Okay. I just made sure they all still loaded. Anyways, I loaded up my main character, exited Lakeview Manor, and used the carriage ride to go to Dawnstar. I killed a dragon, accepted a radiant quest from some ship capatin. Went to the inn, bought some food and mead, went to bed, and started to make my way southwest towards Brood Cavern. anyways, when I was walking there, I quicksaved, then right after that I crashed to the desktop. I tried loading up Skyrim again and I crashed almost instantaneously when I loaded up my quicksave.

Anyways the third time around Steam was able to check if my subscribed mods were up to date, so I deleted the quicksave and loaded my previous save before the Steam issue and I was able to play for about 1 hour with no issues until I got bored.

?So what happened? I should mention that this all happened on my main level 62 character which I've had since launch week and the save file is about 20 MBs right now. Did the Steam error prevent an important mod from being loaded? I have the Unofficial Dawnguard, Hearthfire, Dragonborn, and HD Textures Patches from Steam downloaded and I made sure they were checked to load. Could that have been the issue?

Based off your imformation, it is impossible to tell what went wrong. The cause of the crash could have been a multitude of things. The engine could have choked, mod conflict in some way, your system could have dome something the game didn't like, who knows.

If it didn't happen again, then move on and forget about it.

Well I doubt its a mod conflict, I've been running the same set of mods for a couple of weeks with BOSS and its worked fine. Maybe it was related to the Steam issue? Apparently its a glitch on Steam's end.

So what details would you need?

I had the same problem, and it persisted even after uninstalling all mods. I ended up having to do a fresh install.

I wish I could help you out more, although I can tell you that my problem was unrelated to Steam. As Echonite said though, such a problem can be caused by just about anything. CTDs are really quite annoying.