ESXI 4.1 - HP Flash Drives and N68-S ASRock Motherboard A "No Go"

Could not get ESXi 4.1 to boot on a HP flash drive or SanDisk on a ASRock N68-S system. It would only boot maybe 1 out of 8 times. Definitely not production ready with this setup. Moving back to hard drives in RAID 1.