Exact same thing happened to me. Exact same Sony response.
See my thread (search for lcd massive dead spot)
http://reviews.cnet.com/5208-7813-0.html?forumID=69&threadID=108968&messageID=1240684
Good luck.
HELP!! I bought a sony VGN-S580 ON SEP 12 FROM THE SONY SITE FOR 2700$. I ALSO BOUGHT A WARRANTY FOR 163$. ON NOV 4TH I NOTED THAT THE SCREEN APPEARED TO HAVE AN "INK BLOT STAIN ON THE LCD SCREEN. ISENT IT TO SONY-THEY'RE SAYING I PHYSICALLY DMAGED THE LCD SCREEN AND WANT ANOTHER 750$ TO FIX IT. I DID NOT DAMAGE THE SCREEN. ANYBODY HAVE ANY IDEAS OR SIMILAR PROBLEM?? THANKS

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