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Passive cards are rather finicky, and considering the 9600 is quite powerful it will get hot. If that is your card, you really have to make sure you're getting good airflow around it. If your card is an actively cooled card (with a fan) this still may be the issue. Try gaming a bit with your case side panel off and see if you still get the crashing issues. If it does help them a good case intake or exhaust can help. Always monitor your temperatures! And posting them with your problem helps eliminate that factor.
Hopefully it hasn't been permanently damaged.
Edit: This has now been moved to computers, video cards and leadtek 9600 gt series.