Re: GTx 280 pink screen crash on first running 3D game from 2-3 hours rest.
RMA the card if you want to get rid of this. I have exactly the same problem but since I have 3SLI config I could isolate it. Only one of my GTX 280 cards causes this. It is _not_ overheating, neither power supply or anything else. It is the card. Generally it is not totally broken but right at start cannot run at full frequencies (so quick fix for people having this problem is simply underclock it a little).
Mine after the start when it is cold (was off for a longer time) works ok at 602/1204/1000 clocks but crashes even at standart (602/1296/1107). To make it work stable it is not sufficient or even necessary to (fully) warm it up. You have to let it run for about 3-4 minutes to slightly warm/whatever up (it doesn't even have to run some heavy 3D application, however it does need some warming/time), then turn off and on PC for just a slight moment (sleep on/off is enough). After this all is _perfectly stable_ and I can even easilly overclock it to 675/1350/1242 with absolutely no problems at all.
Just warming it up won't solve the problem. Even if you'll run full 3D for hours underclocked getting the whole system to high temperatures, once you increase the clocks you'll crash. You _have to_ do this on/off thingy to get rid of the problem and you can do it after just a little warming. You don't have to wait long. After that all will be ok.
Either way since only one of my cards causes this it is _definitely_ some hardware problem. My wild guess is some defected part needs to charge and reset (some tyristor or whatever to provide additional line of correct power supply to the chip or something so it can run stable even at higher frequencies).
I didn't RMA it myself since I'm quite happy with my cards overclocking and temperature-keeping abilities and at "standart" clocks this happens only in certain games to me (typicaly WoW title screen reliably crashes immediatelly if this problem is there) so I might have problems to prove my case and I'm not in the mood being without one of my cards for some longer time. I wait until it dies for good then I'll RMA it. If not I can live with it, GT300 is commng soon anyway. :-D However the problem I have now for three-four months and it doesn't seem to get worse.
Usually after PC start I just read some web first then I simply do sleep on/off and can run at even 675/1350/1242 without any troubles. Or if I want to play immediatelly I have Riva Tuner shortcut to underclock it temporarily to stable 602/1200/1000.