make sure you are following this guide
Code:
Menu->Setup->Network->[Blue] button ("Update")
or
Download an image file (from here.)
Place the image file into the root folder of the USB mem. stick
Rename the image file to exactly this: TM800_update.bin (lettercase is important!!!)
Power off at the back.
Power-on and as soon as the front display says "Technomate", start pressing (press-release-press-release, etc.) the "Power/Standby" button on the front pannel,
untill you see "MinoRoot" in the front display - now stop pressing anything, and wait
untill you see something like "<xxx.xxx.xxx.xxx" in the front display, where the xxx.xxx.xxx.xxx is usually 127.0.0.1, or whatever your receiver's current IP address is at the moment.
Now, press the "Menu" button on the fron pannel and observe the rapidly changing letters and numbers in the front display indicating the progress of the image load.
Ideally, at the end of the falsh, the box should restart and take you through the "1st time Wizard".
If not, try a later image.
If that still doesn't help, definitelly do a factory reset before you re-flash again.
thanks to fdlsys from his post here
Code:
http://www.vuplus-support.co.uk/showthread.php?1380-Downloading-TM800HD-Images