Believe 55 is a memory problem, should be in the mobo manual with the error code list, if it won't start with either stick in slot one and the other stick won't either, then prob CPU or mobo (though could be PSU, code makes me think otherwise. Might pull CPU and check for debris/thermal compound on bottom or in socket, reinstall, when installing the heat sink just make it snug, don't tighten down hard (as many people do) and give it a try.....if no joy, I'dpull everything and basically do a bench build, troubleshooting as you go, (problem may be a short from a missing/loose standoff or screw)....have a short little guide I wrote here:
http://www.gskill.us/forum/showthread.php?t=11279