When I try starting the game at the default settings, running it as an administrator, it goes back to the main menu. The only part of the game I see is "Loading..."

Info? OS? Computer specs? Where installed? Using Galaxy or not?

I have same symptoms with latest version (222215). Game is unplayable beyond main menu: it tries to create world, then kicks you to menu. Also it doesn't see your previous save files and unlocked characters.

It looks like they silently dropped Windows XP support in patch 222215. I contacted Klei developer on forum, he said they'll look what can be done and that's it. *silence* ¯\_(ツ)_/¯

I downloaded previous versions of DS and it's DLCs from Humble Bundle (they rarely update theirs installers there, fortunately, in this case!). They work as they should.

In your case, you can use GOG Galaxy client's feature called Rollback. It allows you to download older version of the game, if it is available at GOG (i see no reason why it shouldn't - game is present here quite for some time and it definitely got some updates from Klei).

Interesting how we have Don;t Starve but not Oxygen Not Included.

Oxygen Not Included is an EA game .

Klei: https://www.klei.com/games/oxygen-not-included

Unless I'm missing something.

Been sitting on their update page everyday:

https://forums.kleientertainment.com/game-updates/oni-alpha/

Early Access, not Electronic Arts.

I guess that's a good reason to use InDev instead of Early Access :D

A little heads-up for XP users:
Windows XP support was fixed in one of the latest patches (246924)! I have no problems with running Don't Starve with "Reign of Giants" and "Shipwrecked" DLCs on Windows XP.

By the way, a DLC called "Hamlet" is coming in Q1/Q2 2018. =)