Three times now I've been on surfaces requiring Mud and Ruts setting and on returning to better ground, I've gone through GGS to normal mode on Terrain Response control (step by step or all at once - done both) and the HDC keeps blinking at me when not in first or reverse and information says "HDC not available in this gear".
The steering graphics don't appear but the car feels and drives as it does in M&R so I don't think the Haldex has let go.

I've put it back into M&R and out again, stopped and reversed (as used for wind up in diff lock), stopped the car switched it all off and back on but nothing drops it out except switching off and waiting 6h (as with all TR settings, it remembers what you were in for that long and then restarts in "normal dirving".

My car has full LR dealer history and all available software updates
Has this happeneed to anyone?
Got a fix?

Cheers
Chris Gone... 2013 XS TD4 Manual Firenze Red
Gone... 2008 (09MY) XS Td4 Manual Stornaway Grey
Prior... 2003 G4 Discovery 2, 1998 Disco 1 and 1997 Disco 1 Company car before that
Also gone in Nov'13, after 7.5 yrs, to new owners with time for more TLC - 1980 Series III 88
Current 2015 Discovery Sport HSE 2.0

I think this happened to me a while ago. As far as I remember I just switched off the HDC manually and all was well. No odd warnings on the display. I thought I might have hit the switch accidentally, but it could be as you describe.