The problem with those calculations is not so much the number or frequency of mutations but the restriction of the target sequence to only one possible functional protein out of many hundreds of thousands. If the question gets extended to abiogensis, as happens frequently, other factors that affect the probability calculation are ignored, including the tendency of some molecules to spontaneously combine.
This was a case of a little friendly fire; it's all been cleared up (freepmail). We are all on the same side here. :)