First build. Screen crash then no signal

[lane2905]

Built first gaming rig a week ago. Everything installed correctly. Pc running perfectly for 4 days then when I started playing a game on ultra the screen crashed and then got no signal, but the pc carried on running. Tried resetting it but nothing worked. So turned off. When I turned it back on, I got one short post beep but no signal to monitor. It also didnt seem to boot into windows without signal. Went through all the usual troubleshooting, mem test on motherboard, reset CMOS, removed battery, etc, etc. still no signal. Tried different cables but still the same. Everything seems to be ok, all cables connected correctly, ie gpu, fans, etc, etc. all fans are running including gpu. It powers on with 1 short post beep every time. My parts are: CPU - fx6300 MOBO - asus m5a97 r2.0 GPU - xfx r7870 le (Tahiti) PSU - ******** PowerStation Gaming 500W Silent ATX2 Modular Power Supply MEM - g.skill ripsaws x 8gb 2 mods
I'm thinking it might be GPU, but would like some advice from you guys first before I send it back.

 

[lane2905]

I'm afraid not. That's the problem I've got. Can't test my components on other machines. I'm pretty sure all my other components are fine due to the test I've perform with them. Eg mem test on MOBO, reset CMOS and removed MOBO battery to reset it. I'm also getting the short post beep, it all points to the GPU I think!!!!!

 

[lane2905]

I'm afraid I have no integrated graphics on my motherboard, so I cannot test.
Tried other ports and tried putting GPu into other pci slot, still no signal. The fact it gives me one short post beep suggests that the CPU, memory and motherboard are fine. The psu seems ok as it powers everything ok. This has completely stumped me.