Anomaly on new build

[armedtoe]

This build is about a month old... Here are the specs:
Intel i3-2100 Processor (not overclocked)
ASRock z68 Extreme3 Gen3 Motherboard
4gb 1600mhz Ripjaws (2x2GB)
OCZ 80+ Certified 550W PSU
500GB Seagate 5400RPM Hard drive
Sapphire Radeon HD 6850
AT Case salvaged from old computer
I have overclocked the 6850 up to 900Mhz, using Trixx, and after many days of research into the potential and danger of overclocking it.
THE ANOMALY:
I was playing minecraft, with Firefox playing Youtube in the background. Then, my screen went blank, I lost audio, and a fan in my case went to full speed (likely graphics card, as I have heard it reach full blast before). There was a burning smell (which may have simply been my imagination), and I quickly force shut down my computer. On startup, there were no problems and I cannot see any now.
Is this a precursor to a graphics card failure? I have done some research, and "black-screening" has occurred by playing youtube inside firefox, but I cannot seem to recreate this scenario. The rapid increase in fan speed leads me to believe that it was a hardware problem.

 

[legendkiller]

There's nothing wrong, It's either your video card is causing black screen or your system froze(most likely)... Recommend you running some test see which one freezes...

 

[smorizio]

there open hardware monitor that i use to look at gpu and cpu temps and power supply voltages. prime 95 or intel burn in will stress your cpu. Memtest will test your ram..there are a few gpu test. on the burning part..your nose and eyes are the best thing to look for burn marks or smell cooked parts. i would look at the video card first to see if it was the power circut in the gpu..if the gpu gets to hot it can cause what called a thermal runaway..most gpu and cpu should shut down to stop this..sometime it works but if the card parts are made cheaply or the bios is not set right you can burn parts.

 

[armedtoe]

Best answer selected by armedtoe.