I had a similar issue last summer.the windscreen on my 01'Disco was delaminating(seperating) in that very spot. I noticed a white areat about two inches long right above my mirror.My Disco has the heated windscreen which is about $700 to replace.The dealer deemed it a warranty issue and concluded that this area must be flex point givin the height of the roof.It did'nt make much sense to me, but I did get a new windsreen covered under warranty.