I haven't taken the car to the dealer yet but have discussed it with my service tech. Apparently it is okay to drive the car in two-wheel mode. If there is a more serious problem the car will shut itself down. Unfortunately the car drives like sh*% in two-wheel mode.
I have also researched this extensively on the LR forums. The bad news is that this has been happening since 2006 on pretty much all models, RR, Freelander, LR2,3 &4 and Evoque. There seem to be various causes: low battery, software glitches, bad rear-differentials, even some complete transmission replacements. There doesn't seem to be a universal solution and often requires multiple trips to the dealer. You'd think they'd have a fix for this by now...
It happens in both Sport and Drive modes and is particularly annoying when it kicks in on slippery surfaces (which fortunately has only occurred once). Again there is no common denominator other than acceleration which can be a lot or a little. It rarely happens soon after a cold start but again hot or cold ambient conditions and length of drive time all vary. Sometimes you can stop/start and it goes away the rest of the day or it may come back within a mile or two.
My car did not come with In Control - not sure why, maybe I didn't elect that option but it may not have been available at the time of my order - December 2014.
I'll post back whatever else I learn but won't be going to the dealer until 11-Jan unless the problem becomes more frequent. It has happened on each of my last several drives so I may not be able to wait that long. It sucks driving in tw0-wheel drive mode - if I had wanted a two-wheel drive car I would've bought one.
Ranchos - what would the OBD II scanner tell me that I could use to get this fixed?