The "unknown defect" is the mainboard's northbridge.
HP Pavillion DV2000, DV6000 and DV9000, as well as many other laptops that use the Nvidia 6150 chipset (NF430), nvidia 8200 or GT 102/105, have BGA balling issues. The chipsets overheat and the chips lose a pin or two, bricking the laptop.
I know because i fix these things for a living.