Do a force update.
Update your minecraft.
the demo? you play it like you play minecraft just do what it says
From Minecraft Wiki... it says this Wednesday (October 24th 2012) but I am still not sure.
First, You go to minecraft.net and then click the link that says download. Scroll down to the section that says Multiplayer. click on the link that says Minecraft Server.exe Download and enjoy with your friends :)
There is an option on the downloaded version that says "play offline" click that.
There's nothing on the site that says residents from Illinois can't buy Minecraft.
Once you open minecraft, click "options" then click "Force Update". Then it will work, but the first time will take awhile.
hit log in offline.
At the top right corner, there is button that says sign in.
force update minecraft to clear all your mods then if you want try again.
only if you download the free version of minecraft then look for a specific mod that says minecraft.freeversion
If you go to the website right underneath sign in there should be a button that says play minecraft for free.