You should use a software called Morly's STB Admin Tool (MAT). You'll find attached a 7z archive containing everything needed to run this software.
You just have to put your box in rescue mode (just after powering on, push on the "vol+" button until the VFD indicates the IP address) then you run MAT 2.4.4.1. Push on "Connect" (after entering the IP address) then it's straightforward (flash image uncompressed).
