Did you try the public preview.
To get back to the live build, in the steam properties, right click on the Game Guru icon and choose properties.
Beta tab and choose none or opt out of beta.
Accept that, then See if it ques and update.
Press launch and the files should download.
Sometimes it is a little tough and closing down Steam will be needed.
Hope this helps.
Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz, 2400 Mhz, 4 Core(s), 4 Logical Processor(s), 8gb RAM, Nvidia gtx660, Windows 7 Pro 64bit, Screen resolution 1680 x 1050.
