Fried ECM

Hello all, Installed new distributor with blue ECM, new ballast resistor, and a new OEM coil. Fired up engine, set the timing and let run for five minutes or so. Started engine again, and it died within 30 sec.
Un plugged the ECM from the dist. checked for spark with key on run and had nothing. Any idea why I fried this ECM. Don't want to fry another one . I had the LT blue ECM wire to the same side of ballast as the VR. opposite the coil pos. side. Could this be the problem. Working on 68' Chrys. 440 engine. Thanks in advance.