I have the same problem with a 7025. Interestingly it happens a few weeks ago to after working fine for over a year.

For lack of a better idea at the time, I swapped the PSU for a new unit from a 7025+ (including making the necessary changes). However, it still behaves the same.

I can turn it on or off using the front panel button and from the remote control. But there's ethernet is dead, no signal at the serial port and it won't spin the HD up. The display backlight lights up, and the LCD is showing a full light gray background.

If anyone has any ideas, I'd love to try anything to get this box running again.

Thanks!