I am plugging my external Azden mic directly into the 60D with an XLR to 3.5mm adapter. I have tried recording with both ACG and manual levels. The levels read fine and pick up the mic fine but when I play the video back all I get is a loud hiss that drops out slightly when I am talking but there is nothing but the hiss.
My first thought is the problem has to do with power....does your mic need a battery installed and, if so, is it fully powered?
Perhaps the mic is designed to run off of Camera power which your DSLR may not be able to provide,...I'd try another mic that you know is working just to see more clearly if this is a mic or a camera problem.