Ancestral Allele and Hapmap
It is kind of confusing.  Here's the sequence, from the ncbi link

GGACATTTAAMGAGGTACGTG

So M is "A or C"

Its a missense mutation, the amino acid called for is either an N or a K.  

GGACATTTAAAGAGGTACGTG = K amino acid

GGACATTTAACGAGGTACGTG = N amino acid

GGACATTTAAGGAGGTACGTG = K amino acid

GGACATTTAATGAGGTACGTG = N amino acid

When you blastx it, the top hits are all the K allele, across a few species.  

When you blast the DNA, the non-human hits in nr all have a G, not an A or C.  So I guess that's why they are calling that the ancestral allele.  The human hits to nr all have A, so the K amino acid is conserved.