The version of openblas in the science overlay is quite old, the newest one in the webpage is 0.2.11. Just a name change of the ebuild works for me. I didn't see anything fishy in any of the programs I use with blas (R and octave).
Thanks for the bump request, openblas is bumped to 0.2.11 in the science overlay now.
Version 0.2.12 is already in the overlay, this issue might be closed.