HMC6352 Compass

I had previously purchased a HMC6352 compass and had it sending data perfectly and then all of a suddon it no longer outputed any data and the arduino board and GPS unitt hat I was using said that it could not find compass data. I thought that they actual compass board may be bad so we bought another, but did the same thing to the 2nd board. Before we lock up yet another compass does anyone have any idea what we might be doing to cause this problem??