As from Jan 1 2011, all minifig magnet sets have been glued by LEGO to the magnet base, and the legs and torso are glued as well. Using a box cutter or screwdriver can separate them, but is dangerous and does damage to the minifig usually. Several solvents have been tried, and the best solution for separating them is ... hot water!
Not boiling water, as the ABS plastic they are made of melts above 80 degrees apparently.
There is a method described by thebrickblogger.com
Check the full article out at this link: thebrickblogger.com