An other note:
Your Xbox 360 warranty is extended every time you get a replaced console. I am a super casual gamer and had my launch Xbox 360 RRoD this summer. It was no big deal, and customer service was great. The replacement arrived in less than a week and I even got some free arcade games and Xbox Live coupons.
Downloading software cannot cause your system to instantly overheat and RRoD. If anything it’s the 4 rings of light which means a display cord issue.
...
One alternative reason may be:
Xbox360 is exploitable on a very old firmware version. Exploitable as in "homebrew enabled". MS found out, they included some special procedure in the update which blows a special fuse on the motherboard (e-fuse).
People with older 360's found a way to keep the fuse in-tact (by removing a particular resistor from the MB).
It seems that if you have the resistor removed while installing the nXe - it bricks giving you ...
Final note:
Think about it for a minute.
Tens of thousands (possibly hundreds of thousands),
got to get into preview programs for the NXE and got it early.
There was no outcry until today.
This leads me to think that PS3 fanboys are fueling more of these "fake" reports of problems.
Everyone I know has had NO problems updating.