In the second video, the we see the classic burning alcohol trick in the shortest form I've seen. The commentary is by a third party (mother?) who is wondering why there's a little tin cup with an open flame sitting on the motherboard of the laptop computer. BGA solder failure was a known manufacturing defect on some runs of Apple iBooks and IBM T series laptops, and probably others besides. People worked out that the video processor BGA contacts were the problem by physically pressing on the chip and seeing their video work. The first attempt at repair is usually jurt jamming something non-conductive between the chip and the case to keep the contacts pressed together, but that fix usually stops working after a while, so reflowing the solder becomes the only solution.

-- http://www.ifitjams.com/2008/08/reflowing-solder-under-bga-processors.html