Some Mac users have recently been having problems logging onto any of the Oxford wireless networks. Apparently this is due to an ‘upgraded’ piece of software, Mac OS X Lion. The Bod Law Library has some ways to fix this here: http://lawbod.wordpress.com/2011/11/18/maclion-wifi-issues-with-safari/ and there’s another possible work-around here: http://osxdaily.com/2011/11/06/lion-wi-fi-problems-solution-mac/
Good luck!