I have heard this before, but I have never seen any evidence of it. Do you have a link?
http://www.theobamafile.com/obamacolb.htm
It was widely rumored but apparently no one has seen an actual copy of her COLB, but looking at the link above, pay attention to the comment about Act 96 which permits foreign born children to have a COLB issued up until the 1970’s.
There is no Hawaiian birth certificate