Just observed the following, (which maybe also throw some light on a similar "disk missing" issue. http://myhumax.org/forum/topic/disk-disappears-after-power-cut#post-34952)
There appears to be a bug when the "Power On Timer" is used, which seems to power up the tuner but not the disk....
A couple of days ago I set the PVR to power on at 17:45 so it was up and running when I got home from work.
However pressing the <Pause> button to pause live viewing now gives a "circle with a cross" in the top RH of the screen (presumably meaning action not allowed) and there's nothing showing if I select <Media> to view recorded programs etc.
If I cycle the box off & on with the <Power> button, normal activity is resumed with everything working as expected: Live program Pause; Rewind; Recorded programs are visible etc.