I have a sneaking suspicion that the new XC 70 bus has the common (universal?) rear diff issue so it's going to the Man next weekend to check. No matter if that's the case, it's very much under warranty.
Expensive job, much more so than the same part in the Freelander 2, which has the same part, same issue, but where it's not buried behind a mini subframe that needs removed before removing the diff.
Once fixed, it's good for life. Cause? Too much pressure on the nose bearing meaning it breaks up and showers it's mates in the housing with swarf, too.