The Xbox 360 Slim solved the issue, by totally redesigning the main board, GPU and processor.The Rogue Wolf said:Did they ever sort out exactly what was causing all the failures? I mean, Microsoft isn't a neophyte in the hardware sector, but to see so many units have problems speaks of a serious design flaw.
Microsoft never admitted specifics, but the consensus is that Microsoft designed the 360's GPU chip in house instead of going to Nvidia or ATI. Either through inexperience or cheapness Microsoft did not properly test the chip's ability to cope with thermal stress and they also didn't get their manufacturing up to the kind of standard the big two employ for their chips, it's been alleged that in early production as much as two thirds of chipsets made were defective.
The end result of that was that the GPU of the 360 ran extremely hot, so hot that it would bend under the stress and pull itself out of it's soldered joints to the main board over time, leading to the RRoD. The various minor redesigns of the 360 never addressed the GPU design for whatever reason until the 360-S came out, the 360-S was essentially an all new console.