Strange update - i was inspired by the following thread about a completely different board (even by a different manufacturer): http://forums.overclockers.co.uk/showthread.php?t=18392309
to try something a little odd.
I get the same result as that guy though. Put RAM in slot 3 or two sticks in 3 and 4 and it boots (not tested into windows, got no HDD connected, but it goes to BIOS fine). Any 2 sticks in slots 3 and 4 works so it can't be their fault I guess.
Put any sticks into slots 1 and 2 and it doesn't work, I get the '55' error.
No idea what that means or what to do now, any help? If the OP tries this and it doesn't work I will start a new thread cos I guess it will be a different issue.