Nbox 5800sx struggling

I have an nbox 5800sx which I had working and have since buggered it up!
I now cannot seem to flash with a new image.
when it boots it comes up with U Boot 1.3
when I hold down the up arrow on power up there is no update option only usba usbb hda1 hda2 hda3 pktn(I think and nand.
I have tried to go for usb a and b and pressing ok then it says load but nothing happens.
please can someone help out a halfwit novice as I'm no pulling my hair out!!!!

thanks

I think my problem is that I inadvertently updated the EPG to flash as it now cannot open EPG.dat, however all my channel are there as when I use webif ad look at all channels I can change to any. cant continue using my laptop as a remote for the tv though!
is there any way I can delete the files written to flash to get it back?
thanks to anyone listening!