My Book Studio Ed II firmware will not install bec/ thinks some other usb device still is plugged in

My Book Studio II Firmware Update - PC  Trying to install this download.  Installation starts scan and repeatedly gives the message to unplug all usb devices except the WD hard drive.  I have already unplugged everything, including my mouse.  Several times, I have restarted the computer (Windows XP, desktop) with no usb devices plugged in.  Computer Management does not show any usb devices plugged in.   How do I reach the point at which I will be able to install this firmware? 

Thank you for any help.

4:35 p.m. addition:  I did get the firmware update installed.  I’m not sure what happened; And I was able to use my mouse in the process. 

Thanks anyway.

Did you ever work around this issue?