Same think happened to me in my 2006 LR3. Turns out the inside elbow of the passenger side drain ****** had a leak (pretty much disintegrated!) and water was flowing into floorboard and sill. This caused a connection in the sill to fail and the exact same symptoms you are seeing. Fix was to re-do the connection and bought a new hose/****** combo part and replaced only the ****** as existing hose from sunroof was fine. Everything back to normal after and did the driver's side too as a preventative measure. Good Luck!