it sounds like your card might be bust, but just to see if its a last resort try and reset your motherboard by either removing the cmos battery and putting it back or moving the circuit breakers on your board. it will tell you how to do that in your motherboard manual
It's normal at bootup for a 4870 x2 to have 3 leds light up for a second, shut off, and then have the center led blink once. If they stay lit or keep blinking, there is a problem. That said, I too have suffered from a 4870x2 that died a sudden death. It's not fun.
I'd recommend you try these steps before assuming the card is dead. Test after each step.
1 - turn off PSU and then back on
2 - remove/reconnect the 12V PCI-e power cables
3 - reseat the card
4 - try connecting to the other DVI output on the card
5 - try another monitor
6 - try an analog adapter to a dsub analog monitor input
7 - if possible, try another PSU...and/or ... try the card in another PC with a suitable PSU. edit: Also, try another video card in your system.
If all these still = failure (like with me), it's not looking good for your X2.
Are you using the 1100W PSU in your system config?
I tried all of the steps your mentioned short of trying a new PSU, but i took the system to a friends place and borrowed his Video card and the system booted fine. And i got a 1000w Corsair powering the system.
How did your card die??
I am returning the card today, fingers crossed i get a replacement via warranty.