Mine has today started to go pear shaped as well.
After being on for about 4-5 mins (dashboard or in game), it feezes and the whole screen has a slight pink chequered flag pattern on it. Also if I put my hand to the back of the unit it feels very warm considering its only been on a few mins. Never had any ventilation/heat issues since purchase.
Once I reset it it does the same thing or I get 3 red quadrants on the front circle of light. I reckon it means it is knackered ( I am gonna wait till tomorrow).
Bought it in a branch of GAME, called them up and they said just need to bring it in and if they can reproduce the fault they will just swap the main unit over (not cables, HDD etc).
Just gotta find the receipt now!!! Bought it in 2nd Week of december I think.
Thankfully a visit to the store will sort this out as I didn't fancy being 360-less with SF2 coming out on Tuesday!!!
rp2000