[Unbelievable]

You're quite right. In my hurry to describe the problem I made it sound like the same one. The original post on this thread was a subtley different problem, but I've not seen it occur in months so I'm guessing it's either been fixed or Blizzard have changed whatever it was that caused the problem.

The new report fits under the same title and has similar characteristics, the differences being that the new problem is 100% detail map related (rather than a mix of the two at the same time). The new problem is zone wide, where as the old one was very localised (to roughly single sub zone).