bp put some sort of lock into emu. if there isn't a certain amount of roms it don't work. if you get the stand alone (i think) it should be fine but he removed this lock from his newer versions... coinops 2 r3.
unfortunetly there's drama of some sort over a 1emu right now with bp and everyone else. get some
then start reading, but you should be able clear this up with r3.