freebsd stable - May 2010 - The USB flash driver can't mount as root on 8.1-prerelease boot

Hi, all

I have a box with a Intel DG45FC motherboard. I use a usb stick as root of  
freebsd 8-stable,
but I found it can not mount root in most interface of my box after kernel  
initialized.
There is only way I can use it: plug usb stick and my usb keyboard into  
two front usb socket
at same time. Any other way for example plug keyboard at back socket or  
plug usb stick at
back socket, will stop at mountroot> prompt.
I wonder is that can't mount usb root problem still unresolved on  
8.1-prerelease?


-- 
The Power to Serve