GoFlex only boot with USB HDD plugged

[leshan]

Hi,
I successfully install Arch Linux ARM install on my GoFlex Net by following this great tutorial 'http://www.Arch Linux ARM.com/index.php5/Hybrid_install_on_Seagate_GoFlex_Net'. Thanks.
But I have a problem now. My GoFlex Net can only boot into Arch Linux ARM install wiht USB HDD plugged. If I don't plug anything USB, GoFlex Net will show blink green light forever and I'm not able to SSH to it.
Is there anyway to boot from NAND or restore to original?
Thanks again.