Quality Control is one reason 360 has so many problems. MS cut corners on every aspect of the 360 development in order to cut costs, design, quality of components, QC etc..
A must read for every 360 owner:
"MS was so focused on beating Sony this cycle that the 360 was rushed to market when all indications were that it had serious flaws. The design qual testing was insufficient and incomplete when the product was released to production. The manufacturing test equipment had major gaps in test coverage and wasn't reliable or repeatable. Manufacturing processes at eall levels of suppliers were immature and not in control. "
"...It just wasn't mature enough. Too many design defects, lack of design margins, immature test processes and equipment, insufficient PB free manufacturing expertise at partner manufacturers who made the mother board."