Hi, I suffered from the same problem for quite some time now. It was obviously a loose-fitting display data connector on the logic board. Re-seating the connector solved it for me.
See http://www.pbfixit.com/Guide/51.16.13.html (middle image) Cheers, -- Michael message composed with VIM - Vi IMproved 6.3 (2004 June 7, compiled Jun 18 2004 11:44:00)
