I know this thread is somewhat "dead" though it is the only post in all of Google that I have seen the same problem.
So, my problem is very similar to what dominic7il stated. I boot up, and no keyboard period...No signs of power/lights/life in the board. On Boot, I cannot enter the BIOS to check the error halt settings. If I have a OS loaded hard drive installed, boot travels all the way to login screen. However, I cannot type in password, because KEYBOARD NO WORKY. I have tested multiple USB and PS/2 keyboards (which work on other systems currently), to no avail. I have tried clearing CMOS (yes I took out the battery AND had the system unplugged from wall), clear-CMOS jumper, different keyboards, power On/Off trick with USB boot yadda yadda, and even another E350N. Same problems persist, and there is no information about what the problem is or how to fix, only posts that there is a problem. In fact, if I could just get into the BIOS, I am sure I can fix...but then again, if I can get into BIOS then keyboard is working, and everything becomes a moot point.
Right now, I am running bare minimum to rule out other hardware conflicts.
GA-E350N
G.Skill RipJaws 16gb (2x 8gb) - I have tried jsut dropping to 1 stick @ 8gb
Seagate SATA 2 320gb HDD
And that is it...no other peripherals