Black screen with (almost) new graphics card

I bought a Sapphire HD 7950 graphics card about 2 months ago. Everything worked fine until one day ago when I booted up my computer... everything booted up (Fans Lights & No system beeping) But I was only getting a black screen, with occasional small white flashes. I tried booting with multiple displays and multiple ports (nothing worked). I also tried changing my bios settings also with no luck. (the on-board graphics work fine when the graphics card is removed from the PC) My power supply is a 600W which is more than enough. Again Everything worked fine until that day. I doubt anything is damaged (I handle everything in my PC with extreme care). And yes all of the AMD drivers are installed. I will try to reply to any questions asap, I'm sorry if I don't reply quickly I have a very busy schedule . Any help on this issue would be VERY much appreciated! (Some PC Specs listed below)
[SIZE=3]Lenovo idea centre K450[/SIZE]
[SIZE=3]600Watt new power supply[/SIZE]
[SIZE=3]Intel® 4th Generation Core™ i5[/SIZE]
[SIZE=3]12gb system RAM[/SIZE]
[SIZE=3]Not shure about the motherboard type[/SIZE]