Haha yeah, if i hadn't thought of it, i'm sure very soon someone else would have fetched it up
Anyway, i'd be pretty confident in thinking your 360 does indeed have a dry joint under one of the BGA components, more than likely the GPU as its a common issue.
You say the heat out the back never got that hot, is that a good or bad thing? personally, as i and everyone else raves on about how much heat it produces, i'd say if yours isn't quite producing it, then its bad, simply because it will be producing the same heat as everyone elses, but obviously in some way isn't getting rid of all the heat like ours.
I'd guess it has something to do with the crappy heatsink MS decided to use on the GPU, in my opinion it is way under specked, and their thermal paste sure doesn't help matters.
This is why watercooling is such a good idea, you can effectively install a waterblock on the GPU and remove the heat away from it, right outside the case where you want it, the problem is, you can't really fit a somewhat decent heatsink to the GPU as the DVD drive is in the way, the original is complete cheap alloy, which is rubbish for a component of this spec, better yet it doesn't even have a copper insert to at least try and help duct the heat from the chip to the heatsink, then it stands about 1cm tall and has one crappy way of removing the heat from it. Obviously they couldn't do much more with it, but lets face it, the whole design is CRAP! Watercooling works so well due to the design of the console as the DVD drive is just in the way too much to do anything else, so basically replacing the stock heatsink isn't such an option.
Now while i could agree watercooling may seem a little overkill, the 360 turns out some serious heat, so much the stock cooling just isn't up to the job unless you live at the north pole, and play it outside all day, so really your not left with much more of an option other than to watercool, which beats having multiple dead 360's on your hands.
I personally wouldn't attempt to clamp down the heatsink on the GPU more than it already is, if you get the error back that points towards it, heat gun it, make sure you do a good job to reflow the solder well, this may very well fix your issue, then take good care of it, as it'll probably never last the same over again.
Good luck
