Thanks for this, I just traded with him (I'm the guy in the mentioned post). I have to wait 15 Days before we can trade for my half of the stuff. Market is blocked with this too. This includes logging into a new website with your steam account, anything that makes you verify the code through email is included with this.
Right, we tried that as well, but if you dont know about the restriction and change and then change back, the restriction still remains.
IE dude above was on his other device, hit the restriction, went back to old device, restriction was in place.
Keep this thread up high so everyone knows. Trading is the lifeblood of this site, and I imagine MANY people (as they are on the Steam forums) will run into the problem.
Also, if you've not changed devices and theres no reason why you should run into this restriction, and you do get a restriction, RESTART YOUR PC. I have a bunch of crap on the market and went to change the price of something, but ran into a market restriction. It just means that the new update hasnt been applied yet. I restarted and all was fine.
I just entered into a trade with someone and he was unable to trade b/c of new Steamguard measures in place that gives you a market restriction if you add a new DEVICE. IE if you get a new PC, you cant use the market for 15 days.
This was just started YESTERDAY
Here is a more in depth thread on the situation
http://forums.steampowered.com/forums/showthread.php?t=3176476
I felt this was important to post here.