Hi everyone,
we had this same problem on our 60" LG plasma....spent ages inspecting the ceiling etc as it happened more after heavy rain. Finally worked out what it is !!!
It is water running down our aerial cable, can be because the cable is old or damaged or not looped proberly before coming into the house. The water comes down the inside of the cable and leaks out near the seam with the connector (ust in one corner of the tv)
hope this helps a few other baffled people..sorry to those it doesnt help
cheers x