http://www.cato.org/pubs/pas/html/pa580/pa580index.html
page 13
Keep in mind that these are "soft libertarians", people that consider themselves economically conservative and socially liberal, but don't necessarily go around trolling message boards with anarchist philosophy.
2004 seemed to be unusually bad for the republican percentage of the libertarian vote. The only worse year was 1992, when Ross Perot, Clinton, and Bush I all got a third (well, I think 2008 will be bad, too).