Something with animation failed to load the animation.
If you did not create any custom media or modified any stock media, then I would try and do a verification of game file cache in the steam app.
If you did modify any stock models or scripts, then I would back them up first, or your changes will be lost.
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.
