It seems that BLAS sdot_ in OX X Lion actually returns "double" instead of "float". I'm using the attached patch with success. Of course, it would need a proper configure test that I'm not in position to provide but Matt volunteered to write. Can any of you (Sean?) running Lion try to reproduce the issue using configure --with-precision=single && make all && make test , and then try my patch?

Sure, I'll take a look at this today.