DM 800 HD se freezed on (dream multimedia)on LCD screen

I tried to flash my original Dream box HD se 800 with a new image but the box freezed on (dream multimedia) on LCD screen.
I tried to switch on/off the box many times at different time with no response.
I tried to communicate with the box through the web, dream up and flash wizard and
Every time I get dream multimedia on LCD screen with no progress (can not access the box)
Any body has any idea where is the problem and how can I solve it?
I got the box for about 18 month and I wonder if the guarantee covers to repair the box.
It bought from Germany.
Thanks in advance