I just set up a new server and kept having a keyboard issue. When powering on, the keyboard worked. When rebooting, it did not.
When I tried another USB port, I saw these errors:
uhub_reattach_port: could not allocate new device
Errors in /var/log/messages showed:
usb_alloc_device: device init 2 failed (USB_ERR_IOERROR, ignored) ugen0.2:
at usbus0 (disconnected) uhub_reattach_port: could not allocate new device
I found the fixed mentioned in a nas4free forum post. The solution: disable XCHI mode in the BIOS.
It took a while to locate that setting. It was under Advanced > Chipset Configuration > PCH-IO Configuration. changed XCHI mode to disabled, rebooted, and the problem never recurred.