BionicAli :
i have the exact same problem with gtx 580 did u find any solution or its the card is dead ?
I baked it in the oven, not kidding. There are lots of ways to do it but this is what I did.
Removed the main fan/heatsink component
Scrubbed off the thermal compound with rubbing alcohol
Set the over to 180 degrees Celsius (preheated)
Put the card on top of two tin foil balls on a baking tray in the oven
Set timer for 9 minutes (people say 5 minutes isn't enough and 12 minutes is too much)
Turn off the over after 9 minutes, but leave the card in there for 15/20 minutes
Open the oven door after 15/20 and leave to cool for another 20/30 minutes
Apparently this allows the card to cool down gradually
Reapply thermal paste and reattach heatsink etc
Apparently the whole process reseats all of the solder joints, which is often the problem with an old card suddenly becoming unusable.
There are a lot of videos on it but this is what I did. Now my card is working like new, not kidding.
Obviously do this when you've tried everything else.