Haven't actually gotten around to playing it yet, might have to give it a whirl sometime soon.

I honestly cannot even remember this game. I swear it was something I think I knew about and wanted but for whatever reason I just forgot about it.

When you mentioned 'Chinese Room' I actually thought of The Chinese Room too, I didn't think that would actually be the hint though. That's a very interesting combination!

I know The Chinese Room are working on an open world exploration game thingy called 'Everybody's Gone To The Rapture' but I think that's a different project. I guess this is the 'game B' project they didn't reveal any info about yet.

Edit: http://thechineseroom.co.uk/?page_id=53. That's definitely their project with Frictional. This is going to be awesome. TCR already did a horror'ish mod called http://www.moddb.com/mods/korsakovia/.

The ARG was solved this morning.
And officially closed about 1:45 pm Easter Time.
The reward was this complete http://www.vgzero.com/game-news-image-2012-8d324dc47717c3a62ff8c3ca76ece138.png
Cryptic messages on the site revealed a title and release date.
It's called Amnesia: A Machine For Pigs, or maybe just A Machine For Pigs.
The ARG site says it will be released Fall 2012.
gameB on the Chinese Room site is said to be released Q4 2012.
Leading to further evidence of Frictional and Chinese Room working together.

Speculation Below:
The concept art features a figure dressed in a certain uniform. He may either be a member of the KKK or one of those Spanish(I think) monks.
The level of technology suggests a more modern time in comparison to the first Amnesia. However, given the creative liberties Frictional has taken, a 1800ish setting is still likely.
I also suspect it will be released as DLC for Amnesia, because Amnesia has an empty DLC page on Steam. And the engine referred to in the ARG was HPL 2.1(Penumbra was HPL 1, Amnesia was HPL 2, HPL 3 is still in development).
It also has been speculated that Daniel will return as a protagonist. I think this is highly unlikely. Amnesia has three possible endings and only one involves him leaving Brennanburg.
There is also very wild speculation that the game will be set in an Underwater city[2] and the main characters name is Simon, there is also monsters that look exactly like big daddies.
This was purported by a strange bit of concept are called Mantis. Supposedly found on one of Frictionals sites....
The site is blocked and the original finder is the lead editor of the Bioshock wiki[2].
Put 2 and 2 together and...
...I personally think he made it up to get attention.
However, there is a large portion of people that have been convinced by him. I'm just giving you a heads up.

I'm pretty sure we can expect an Official unveil soon. Hopefully with a trailer and some screens. To quell some of those wild speculations.

Edit: Fixed link.

Well my girlfriend bought me the windows version about a day before my system got wiped an I installed linux to replace it. Now I cant get the windows version of Amnesia working so I'm just going to wait to get a pc. It's so tantalising, Amnesia just staring at me from my games shelf.. luring me... whispering to me..

Picture doesn't work.

Huh, I can see it.

Edit: It may be because I am a member of the FG forums.
I found another http://www.vgzero.com/game-news-image-2012-8d324dc47717c3a62ff8c3ca76ece138.png. Hope it works.
BTW, I wouldn't recommend joining the FG forums.
There is a lot of drama, especially over the Pewdiepie vs Tanshaydar fiasco.
Especially now there has been a recent increase in members and, as a result, spam.

http://www.pcgamer.com/2012/02/23/amnesia-a-machine-for-pigs-due-later-this-year/

I bought "Amnesia: The Dark Descent" on a Steam sale without doing much research. I live in a castle. An old creaky cold castle with spooky wind noises...With a dungeon... I'm too scared to go down there now.

I went down, and it wasn't nice.

Just an update:

http://www.rockpapershotgun.com/2012/02/23/thechineseroom-working-on-amnesia-a-machine-for-pigs/

I've seen a let's play of this game. Seems good. Kind of reminds me of Darkness Within.

Darkness Within was a pretty good game.
Darkness Within 2 had some good changes, but seemed a lot less scary. Probably because of those very comical character models and animations.

Amnesia and Darkness Within both take on the Lovecraftian Horror style. IMO that is the best style.

http://www.rockpapershotgun.com/2012/03/12/makin-bacon-dan-pinchbeck-on-a-machine-for-pigs/

Wow. How did I miss this? ATD is by far the scariest game that I have ever played!

Although it's not my genre, this looks well done indeed.

I used to play Amnesia, then I got amnesia and forgot how to play.