i have UPS usb plugged in to host, but not pass thru to unRAID.
looked at esxi logs, nothing obvious..
it's part of the syslinux boot loader. see here: http://www.linuxquestions.org/questions/puppy-71/ldlinux-sys-what-does-it-do-942097/
according to this,
"At boot, the computer loads the MBR (/usr/lib/syslinux/mbr.bin). Then the MBR looks for the partition that is marked as active (boot flag). Once found, the volume boot record (VBR) will be executed. In the case of ext2/3/4 and fat12/16/32, the starting sector of ldlinux.sys is hard-coded into the VBR. "
looks like something with your flash as it can't read this sector?