Most of the RROD’s stem from overheating. Just by looking at the design of the system you can tell that the GPU is going to eventually overheat. The GPU heatsink is disproportionately small for the amount of heat it puts out (basically a desktop GPU paired with a laptop-sized heatsink), and you have a huge DVD drive that sits on top of it to further block airflow. Eventually the system heats up and the motherboard starts to warp, which breaks the solder on the chips and essentially disconnects them from the board. This is also why the RROD can disappear and come back; the motherboard can sometimes cool down to the point where it returns to its normal shape and temporarily reconnects with the chips, but after a while it will start to warp again and the problem reappears.
Assuming that the heat is indeed the culprit (and I have little doubt that it is), the only guaranteed fix is to reflow the solder on the chips, and then either ditch the original 360 case for one that moves the DVD drive to somewhere not on top of a heatsink, or install a water cooling system. Simply replacing the clamps or reflowing the chips does not provide a lasting solution because the cooling system itself is fundamentally flawed. These options are also really expensive unless you possess the skill to build/mod the case yourself for cheap.
Luckily Microsoft has finally decided to ditch the old design, too, and the new 360 is pretty much devoid of the heat problems of the old unit. Buying a brand new 360 is really the cheapest option for most people.