I believe the one with the single IC is the latest one. I have two M4's, one I just received and they both only have 1 IC.
Also, I tried to identify the two diodes when I burned up my first M4 by accident. I thought I had it figured out and ordered some diodes off the net. The ones I received were bigger than those on the mother board. It took me a long time to find something that interpreted what MCC and BFE meant. MCC refers to the company Micro Commercial Components and BFE referred to the rating of the diode. I just tried searching again, but can't find it. I believe it is called a "Bi-directional 1500W Surface Mount Transient Voltage Supressor" with part number smcj26ca. The diodes I received in the mail were marked GFE which appears to be the uni-directional version, part number smcj26a.
Ooh, I think I just found it on the MCC website.
I didn't order from these guys so maybe you'll have better luck getting it from the manufacturer. I may try it again just to see if that truly is my problem, although I don't really need 2 M4's. Maybe a backup would be good. This thing seems really flaky.