I have the z87 pcmate with the same error. Have fixed the boot order as suggested. Seems to be a USB device problem. The problem device is a USB hub that also has an integrated sdcard slot and slots for other formats. It is a powered hub and has a keyboard and touch screen attached to it. The problem seems to be the hub itself, but hard to know for sure (yet). Do you support attached hub? Does the card slot cause the problem?
Removing the hub worked. Turning off the two switches improves the results, but it still locks up sometimes. Weird. Trying to just work around the need for a hub. But roadblocked on a display problem at the moment. Thanks.