HP Server and USB Drive Boot Issue

Hello.

I'm working with an HP Proliant DL160 G6.  It has an HP SAS RAID controller with two internal hard drives  - SAS 450GB mirrored.

It's running Windows Server 2008 R2 Standard and Exchange 2010.

Attached to the USB port is a Western Digital "My Book" 3TB drive.

The USB drive is configured as a backup drive for Backup Assist.

A backup is run each night as a Windows drive image backup with the Exchange Server option.

The issue I'm having is that when the machine reboots, it tries to boot from the USB.  when I go into the BIOS, I set the boot order as follows - Hard Drive, DVD/CD, USB, NIC.

If the USB drive is plugged in, the boot up will stop after all devices are scanned, then it stops with a black screen and a blinking cursor.

I tried to set the USB drive in different emulation modes in the BIOS, but that didn't help either.  The odd thing is that there two drives recognized during POST, the "My Book" and a "Western Digital SES" drive.

If I unplug the drive from the USB port (I tried all ports to no avail) it boots up just fine.

This situation makes it impossible to remotely manage the server and restart it after applying fixes.

Has anyone seen this odd behavior with HP DL 160 servers and the WD USB external drives?

Any help is greatly appreciated.

Thanks,

-Ted