Did you have a look at doozan's
forum to see if there's any talk about that ?
OK the seagete plug derivates are not guru plugs ... but here's my 2 pence:
Some six months or so ago I updated my seagete plug like devices to boot newer kernels (by using doozan's updater script) and all can boot from usb flash drives ... but sometimes it fails. Apparently it happened more frequently on one particular device (the dockstar I attempted to add the missing hardware to get hwclock working) so I assumed I might have made some minor dammage on it.
In any case when booting from usb flash drive failed generally restarting usb and rescan usb devices got it working ... sometimes a full hardware reset was necessary to get things right.
My dockstars now boot minimal systems from internal flash while my goflexnets boot from a partition on the sata drives so I made no further investigation in the issue ... but all the tuning before that was done on usb flash drives.
I was actually planning on keeping the system on flash drives but since booting was not 100% reliable I went for something that proved to be more reliable.