Thanks to all who have replied.
Per Ed Hickland's comment/request, I have provided a video of the play in question at the link below.
http://home.comcast.net/~jmvideos/CutBlockPF.wmv
The clip first shows the play in realtime and then in slow motion. The camera angle isn't ideal, but the block is made by the Offensive Center against the Defensive Nosetackle. It looks to me like the center does take a half step back before initiating the cut block. An illegal block below the waist was called on the play and the play had no material impact on the outcome of the game.
After seeing the video of the play, I'm curious as to how many would have called it and how many would have let it go.
Thanks.
JM