A driver issue with the USB stick??
I will now add... it seems my issue was a suspect USB stick.
It is a brand name Verbatim unit, but the Vu boxes have trouble with it.
EG: it can be seen if i am plugging it in with files on it to play, BUT, it can be seen by the boxes if i use the exact same USB unit for Flashing a new image.
It is just ignored on boot up...
It is FAT32. It is just a dodgy USB stick. Sometimes very frustrating when trying to find a fault.