OK, I have a 4GB Slim model (but it has the 250GB hard drive added) and also have the Kinect.
For the most part it works fine. My son plays his Call of Duty and Left 4 Dead games for hours at a time and no issues, and the games I have played have worked fine for me as well.
My wife, on the other hand, has been trying to play Your Shape: Fitness Evolved and is coming close to throwing the 360 out the window! She has a new routine set up where she has 10 workouts back-to-back, and it's set up to track her calorie burn and meet challenges and such.
She gets through about 7 of the 10 challenges and the Xbox just reboots on her. No errors, no messages, no freezing or glitching, just a reboot without warning. It doesn't save her progress in the game either, so she has to start it all over! It has happened every time times she has tried to do it.
I thought it may be something to do with the Kinect sensor drawing too much power from the console, since the console has always worked fine when we play other games, so I tried plugging the Kinect into its wall AC adapter, but that didn't change anything.
I was thinking it was just her game at that point, but I was watching Netflix on it, the episode of the show I was watching ended and I went to the computer to check my email. I came back to find the console had rebooted itself on me too! It was just sitting idle at the Netflix episode select screen! I have also had it happen several times just sitting idle at the dashboard.
I have also tried a different HDMI cable, a different HDMI port on the TV, I tried a different outlet, I cleared out the system cache (this allowed my wife to get through her workout for the first time, but have still had reboots since.)
Last night I left it running on the dashboard to see if it was still happening, only to wake up this morning to the "red dot of death!"
Sorry for the wall of text, but I want to be thorough in what happened. Please bear in mind that it's a solid half hour of strenuous excercise for my wife to "test to see if it it still doing it." Any ideas what could be going on? I'm starting to think I have a defective console.... Thanks for any help!