Thanks to a tip from a libertarian friend, I did a quick search of Anders Behring Breivik's 1500 page manifesto (which you can find here) and he does indeed cite Mises and Hayek in his crazed and offensive ramblings. In addition, he also references three Mises Daily articles from Mises.org.
There's only one cite of Mises, which is in a discussion of the nature of democracy where he also cites Popper. The four citations of Hayek all come from either Road to Serfdom, in the context of the problems of international planning, the size of the state, and personal responsibility, or "The Intellectuals and Socialism," in the context of the "second hand dealers in ideas" becoming progressively more leftist. (He also mentions Hayek as one of the "villains" of Naomi Klein's book.) All of the quoted material is political theory and none of it can in any way be connected to the guy's hatred of Islam, his opposition to multiculturalism, or his justifications of violence and call for a European revolution.
Just thought you should know because it will eventually be brought up by those with nasty agendas.
UPDATE: to be clear, there is absolutely nothing in this guy's ramblings, from what I can see from my skim, that even remotely suggests he desired a liberal order in the sense that Mises and Hayek did (as if his actions weren't evidence enough). This only goes to show that no thinker can control how his or her ideas will be used and by whom. It's a risk we all take every time we put it out there in public.
UPDATE 2: Now it's coming out that hunks of it are plagiarized from the Unabomber.